Showing papers on "Protoporphyrin IX published in 1992"
TL;DR: Preclinical studies in experimental animals and human volunteers indicate that ALA can induce a localized tissue-specific photosensitization if administered by intradermal injection, opening the possibility of using ALA-induced PpIX to treat tumors that are too thick or that lie too deep to be accessible to either topical or locally injected ALA.
Abstract: The tissue photosensitizer protoporphyrin IX (PpIX) is an immediate precursor of heme in the biosynthetic pathway for heme. In certain types of cells and tissues, the rate of synthesis of PpIX is determined by the rate of synthesis of 5-aminolevulinic acid (ALA), which in turn is regulated via a feedback control mechanism governed by the concentration of free heme. The presence of exogenous ALA bypasses the feedback control, and thus may induce the intracellular accumulation of photosensitizing concentrations of PpIX. However, this occurs only in certain types of cells and tissues. The resulting tissue-specific photosensitization provides a basis for using ALA-induced PpIX for photodynamic therapy. The topical application of ALA to certain malignant and non-malignant lesions of the skin can induce a clinically useful degree of lesion-specific photosensitization. Superficial basal cell carcinomas showed a complete response rate of approximately 79% following a single exposure to light. Recent preclinical studies in experimental animals and human volunteers indicate that ALA can induce a localized tissue-specific photosensitization if administered by intradermal injection. A generalized but still quite tissue-specific photosensitization may be induced if ALA is administered by either subcutaneous or intraperitoneal injection or by mouth. This opens the possibility of using ALA-induced PpIX to treat tumors that are too thick or that lie too deep to be accessible to either topical or locally injected ALA.
1,209 citations
TL;DR: ALA may be superior to conventional sensitiser for tumours that produce haem as the PP IX is synthesised in malignant cells while the other sensitisers mainly localise to the vascular stroma of tumours, raising the possibility of more selective necrosis in tumours.
Abstract: Aminolaevulinic acid (ALA) is the first committed step in haem synthesis. In the presence of excess ALA the natural regulatory feedback system is disrupted allowing accumulation of protoporphyrin IX (PP IX) the last intermediate product before haem, and an effective sensitiser. This method of endogenous photosensitisation of cells has been exploited for photodynamic therapy (PDT). We have studied the fluorescence distribution and biological effect of induced PP IX in normal and tumour tissue in the rat colon. Fluorescence in normal colonic tissue was at a peak of 4 h with a rapid fall off by 6 h. The fluorescence had returned to background levels by 24 h. All normal tissue layers followed the same fluorescence profile but the mucosa showed fluorescent levels six times higher than the submucosa, with muscle barely above background values. At 6 h the ratio of fluorescence levels between normal mucosa and viable tumour was approximately 1:6. At this time laser treatment showed necrosis of normal mucosa and tumour with sparing of normal muscle. There was good correlation between the fluorescence distribution and the biological effect of ALA-induced photosensitisation on exposure to red light. ALA may be superior to conventional sensitisers for tumours that produce haem as the PP IX is synthesised in malignant cells while the other sensitisers mainly localise to the vascular stroma of tumours. There is also a greater concentration difference between the PP IX levels in tumours and in normal mucosa and normal muscle than with the other photosensitisers raising the possibility of more selective necrosis in tumours.
277 citations
TL;DR: The preparation from Percoll-purified cucumber of a subplastidic membrane fraction that is capable of high rates of Mg insertion into protoporphyrin IX is described, finding that the plastid stroma was inactive when used either alone or in combination with the membrane fraction.
Abstract: The preparation from Percoll-purified cucumber (Cucumis sativus)etiochloroplasts of a subplastidic membrane fraction that is capable of high rates of Mg insertion into protoporphyrin IX is described. The plastid stroma was inactive when used either alone or in combination with the membrane fraction. Successful preparation of the subplastidic membrane fraction required that Mg-protoporphyrin chelatase was first stabilized by its substrate. This was achieved by lysing Percoll-purified plastids in a fortified hypotonic medium containing protoporphyrin IX prior to ultracentrifugation and separation of the stroma from the plastid membranes. Protoporphyrin IX became membrane bound. Other additives needed for enzyme activity fell into two groups: (a) those needed for enzyme stabilization during membrane preparation and (b) those involved in the primary mechanism of Mg insertion into protoporphyrin IX. Ethylenediaminetetraacetate belonged to the first group, magnesium belonged to the second group, and ATP belonged to both groups.
185 citations
TL;DR: It is concluded that the hemEHY gene cluster encodes enzymes for the synthesis of protoheme IX from uroporphyrinogen III and probably constitutes an operon.
Abstract: Mutations that cause a block in a late step of the protoheme IX biosynthetic pathway, i.e., in a step after uroporphyrinogen III, map at 94 degrees on the Bacillus subtilis chromosomal genetic map. We have cloned and sequenced the hem genes at this location. The sequenced region contains six open reading frames: ponA, hemE, hemH, hemY, ORFA, and ORFB. The ponA gene product shows over 30% sequence identity to penicillin-binding proteins 1A of Escherichia coli, Streptococcus pneumoniae, and Streptococcus oralis and probably has a role in cell wall metabolism. The hemE gene was identified from amino acid sequence comparisons as encoding uroporphyrinogen III decarboxylase. The hemH gene was identified by enzyme activity analysis of the HemH protein expressed in E. coli. It encodes a water-soluble ferrochelatase which catalyzes the final step in protoheme IX synthesis, the insertion of ferrous iron into protoporphyrin IX. The function of the hemY gene product was not elucidated, but mutation analysis shows that it is required for a late step in protoheme IX synthesis. The hemY gene probably encodes an enzyme with coproporphyrinogen III oxidase or protoporphyrinogen IX oxidase activity or both of these activities. Inactivation of the ORFA and ORFB genes did not block protoheme IX synthesis. Preliminary evidence for a hemEHY mRNA was obtained, and a promoter region located in front of hemE was identified. From these combined results we conclude that the hemEHY gene cluster encodes enzymes for the synthesis of protoheme IX from uroporphyrinogen III and probably constitutes an operon.
134 citations
TL;DR: The pattern of photosensitisation in the normal rat stomach is studied using di-sulphonated aluminium phthalocyanine and 5-aminolaevulinic acid as photosensitisizers and its photodynamic effect was essentially confined to the mucosa.
Abstract: Dysplasia in the upper gastrointestinal tract carries a risk of invasive malignant change. Surgical excision of the affected organ is the only treatment available. Photodynamic therapy has been shown to be promising in the treatment of early and superficial tumours and may be useful for the ablation of dysplastic mucosa. Because of the diffuse nature of the disease, such treatment would necessarily involve destruction of large areas of mucosa and it is desirable to confine its effect to the mucosa in order that safe healing can take place. By means of photometric fluorescence microscopy, we have studied the pattern of photosensitisation in the normal rat stomach using di-sulphonated aluminium phthalocyanine (AlS2Pc) and 5-aminolaevulinic acid (ALA) as photosensitisizers. AlS2Pc resulted in a panmural photosensitisation of the gastric wall with the highest level encountered in the submucosa. The mucosa and muscularis propria were sensitised to equal extent. Following light exposure, a full thickness damage resulted. ALA is a natural porphyrin precursor and exogenous administration gave rise to accumulation of protoporphyrin IX (PPIX) in the cells. The resultant pattern of photosensitisation was predominantly mucosal and its photodynamic effect was essentially confined to the mucosa. ALA produced a selective photosensitisation of the gastric mucosa for its photodynamic ablation with sparing the underlying tissue layers.
107 citations
TL;DR: Evaluated data support the view that PDT with topical ALA is a promising approach for the treatment of epidermal cutaneous disorders and a build-up of the porphyrin in the skin.
Abstract: Photodynamic therapy (PDT) is a relatively new approach to the treatment of neoplasms which involves the use of photoactivatable compounds to selectively destroy tumors. 5-Aminolevulinic acid (ALA) is an endogenous substance which is converted to protoporphyrin IX (PpIX) in the synthetic pathway to heme. PpIX is a very effective photosensitizer. The goal of this study was to evaluate the effect of PDT using topical ALA on normal guinea pig (g.p.) skin and g.p. skin in which the stratum corneum was removed by being tape-stripped (TS). Evaluation consisted of gross examination, PpIX fluorescence detection, reflectance spectroscopy, and histology. There was no effect from the application of light or ALA alone. Normal non-TS g.p. skin treated with ALA and light was unaffected unless high light and ALA doses were used. Skin from which the stratum corneum was removed was highly sensitive to treatment with ALA and light: 24 h after treatment, the epidermis showed full thickness necrosis, followed by complete repair within 7 d. Time-dependent fluorescence excitation and emission spectra were determined to characterize the chromophore and to demonstrate a build-up of the porphyrin in the skin. These data support the view that PDT with topical ALA is a promising approach for the treatment of epidermal cutaneous disorders.
100 citations
TL;DR: A Tn5-induced mutant of Bradyrhizobium japonicum, strain LORBF1, was isolated on the basis of the formation of fluorescent colonies, and stable derivatives were constructed in backgrounds of strains LO and I110.
Abstract: A Tn5-induced mutant of Bradyrhizobium japonicum, strain LORBF1, was isolated on the basis of the formation of fluorescent colonies, and stable derivatives were constructed in backgrounds of strains LO and I110. The stable mutant strains LOek4 and I110ek4 were strictly dependent upon the addition of exogenous hemin for growth in liquid culture and formed fluorescent colonies. The fluorescent compound was identified as protoporphyrin IX, the immediate precursor of protoheme. Cell extracts of strains LOek4 and I110ek4 were deficient in ferrochelatase activity, the enzyme which catalyzes the incorporation of ferrous iron into protoporphyrin IX to produce protoheme. Mutant strain I110ek4 could take up 55Fe from the growth medium, but, unlike the parent strain, no significant incorporation of radiolabel into heme was found. This observation shows that heme was not synthesized in mutant strain I110ek4 and that the heme found in those cells was derived from exogenous hemin in the growth medium. The putative protein encoded by the gene disrupted in strain LORBF1 and its derivatives was homologous to ferrochelatases from eukaryotic organisms. This homology, along with the described mutant phenotype, provides strong evidence that the disrupted gene is hemH, that which encodes ferrochelatase. Mutant strain I110ek4 incited nodules on soybean that did not fix nitrogen, contained few viable bacteria, and did not express leghemoglobin heme or apoprotein. The data show that B. japonicum ferrochelatase is essential for normal nodule development.
86 citations
TL;DR: In Epstein-Barr virus-transformed lymphoblastoid cells from a proband with EPP, enzyme activity, an immunochemically quantifiable protein, and mRNA content of ferrochelatase were about one-half the normal level, suggesting that decreased ferroChelatase mRNA is due to an unstable transcript.
Abstract: The molecular basis of an inherited defect of ferrochelatase in a patient with erythropoietic protoporphyria (EPP) was investigated. Ferrochelatase is the terminal enzyme in the heme biosynthetic pathway and catalyzes the insertion of ferrous iron into protoporphyrin IX to form heme. In Epstein-Barr virus-transformed lymphoblastoid cells from a proband with EPP, enzyme activity, an immunochemically quantifiable protein, and mRNA content of ferrochelatase were about one-half the normal level. In contrast, the rate of transcription of ferrochelatase mRNA in the proband's cells was normal, suggesting that decreased ferrochelatase mRNA is due to an unstable transcript. cDNA clones encoding ferrochelatase in the proband, isolated by amplification using the polymerase chain reaction, were found to be classified either into those encoding the normal protein or into those encoding an abnormal protein that lacked exon 2 of the ferrochelatase gene, indicating that the proband is heterozygous for the ferrochelatase defect. Genomic DNA analysis revealed that the abnormal allele had a point mutation, C----T, near the acceptor site of intron 1. This point mutation appears to be responsible for the post-transcriptional splicing abnormality resulting in an aberrant transcript of ferrochelatase in this patient.
73 citations
TL;DR: In this article, the relationship between molecular properties of 24 DPE herbicides and their effects on enzyme-inhibitory and herbicidal activities in barley (Hordeum vulgare L.) and cucumber (Cucumis sativus L.).
70 citations
TL;DR: Proto biosynthesis and accumulation were triggered by manipulation of the porphyrin‐heme biosynthetic pathway and triggered destruction of treated cells within the first 30 min of illumination, probably via the rapid oxidation of cellular constituents by singlet oxygen.
Abstract: Rapidly proliferating transformed mammalian cells can be photodestroyed in vitro upon inducing the accumulation of endogenous protoporphyrin IX (Proto). Proto biosynthesis and accumulation were triggered by manipulation of the porphyrin-heme biosynthetic pathway. Proto accumulation in cultured cells was induced by treatment with 1.0 mM delta-aminolevulinic acid (ALA), a naturally occurring 5-carbon amino acid, for 3.5 h. In darkness, significant Proto accumulation became evident within 3.5 h of incubation. In the light, the accumulated tetrapyrroles triggered destruction of treated cells within the first 30 min of illumination, probably via the rapid oxidation of cellular constituents by singlet oxygen. Protoporphyrin IX accumulation and specific cell lysis increased significantly by inclusion of 0.75 mM 1,10-phenanthroline (Oph), a tetrapyrrole biosynthesis modulator. Slower growing untransformed cells did not accumulate significant amounts of Proto following ALA and Oph treatment unless stimulated to proliferate with the mitogenic lectin Concanavalin A.
68 citations
TL;DR: It is concluded that in FLCs, hemin induces ferritin H-chain biosynthesis by multiple mechanisms: a transcriptional mechanism exerted also by protoporphyrin IX and a translational one, not displayed by protomolecularin IX but shared with FAC.
Abstract: The mechanisms that regulate the expression of the H chain of the iron storage protein ferritin in Friend erythroleukemia cells (FLCs) after exposure to hemin (ferric protoporphyrin IX), protoporphyrin IX, and ferric ammonium citrate (FAC) have been investigated. Administration of hemin increases the steady-state level of ferritin mRNA about 10-fold and that of ferritin protein expression 20-fold. Experiments with the transcriptional inhibitor actinomycin D and transfection studies demonstrate that the increment in cytoplasmic mRNA content results from enhanced transcription of the ferritin H-chain gene and cannot be attributed to stabilization of preexisting mRNAs. In addition to transcriptional effects, translational regulation induces the recruitment of stored mRNAs into functional polyribosomes after hemin and FAC administration, resulting in a further increase in ferritin synthesis. Administration of protoporphyrin IX to FLCs produces divergent transcriptional and translational effects. It increases transcription but appears to suppress ferritin mRNA translation. FAC treatment increases the mRNA content slightly (about twofold), and the ferritin levels rise about fivefold over the control values. We conclude that in FLCs, hemin induces ferritin H-chain biosynthesis by multiple mechanisms: a transcriptional mechanism exerted also by protoporphyrin IX and a translational one, not displayed by protoporphyrin IX but shared with FAC.
TL;DR: Human skin shows a strong autofluorescence in the red spectral region with main peaks around 600, 620, and 640 nm caused by the porphyrin production of the gram positive lipophile skin bacterium Propionibacterium acnes, and photodestruction of PropIONibacteria acnes by visible light appears to be a promising therapy.
Abstract: Human skin shows a strong autofluorescence in the red spectral region with main peaks around 600, 620, and 640 nm caused by the porphyrin production of the gram positive lipophile skin bacterium Propionibacterium acnes. Irradiation of these bacteria reduces the integral fluorescence intensity and induces the formation of photoproducts with fluorescence bands around 670 nm and decay times of about 1 and 5 ns. The photoproduct formation is connected with an increased absorption in the red spectral region. The endogenous fluorescent porphyrins act as photosensitizers. Photodestruction of Propionibacteria acnes by visible light appears therefore to be a promising therapy. The photodynamic activity of the photoproducts is lower than that of protoporphyrin IX.
TL;DR: Results provide clear evidence that in pea etioplasts, [3H]acifluorfen exclusively binds to protoporphyrinogen oxidase, that the protoprophyrinogens oxidase inhibitors tested so far bind to the same region of the enzyme and that this region overlaps the catalytic site of the enzymes.
Abstract: It is now generally accepted that protoporphyrinogen oxidase is the target-enzyme for diphenylether-type herbicides. Recent studies [Camadro, J-M., Matringe, M., Scalla, R. & Labbe, P. (1991) Biochem. J. 277, 17–21] have revealed that in maize, diphenyl ethers competitively inhibit protoporphyrinogen oxidase with respect to its substrate, protoporphyrinogen IX.
In this study, we show that, in purified pea etioplast, [3H]acifluorfen specifically binds to a single class of high-affinity binding sites with an apparent dissociation constant of 6.2 ± 1.3 nM and a maximum density of 29 ± 5 nmol/g protein. [3H]Acifluorfen binding reaches equilibrium in about 1 min at 30°C. Half dissociation occurs in less than 30 s, indicating that the binding is fully reversible.
The specificity of [3H]acifluorfen binding to protoporphyrinogen oxidase is examined. [3H] Acifluorfen binding is inhibited by all the peroxidizing molecules tested. The phthalimide derivative, N(4-chloro-2-fluoro-5-isopropoxy)phenyl-3,4,5,6-tetra hydrophthalimide, exerts a mixed-competitive inhibition on this binding. The effects of all these molecules on the binding of [3H]acifluorfen are tightly linked to their capacity to inhibit pea etioplast protoporphrinogen oxidase activity. Furthermore, protoporphyrinogen IX, the substrate of the reaction catalyzed by protoporphyrinogen oxidase, was able to competitively inhibit the binding of [3H]acifluorfen. In contrast, protoporphyrin IX, the product of the reaction, did not inhibit this binding.
All these results provide clear evidence that in pea etioplasts, [3H]acifluorfen exclusively binds to protoporphyrinogen oxidase, that the protoporphyrinogen oxidase inhibitors tested so far bind to the same region of the enzyme and that this region overlaps the catalytic site of the enzyme.
01 Jan 1992
TL;DR: Porphyrins are highly coloured compounds which fluoresce red in light of wavelength around 400 nm, which are essential for all biological oxidation reactions.
Abstract: Porphyrins are highly coloured compounds which fluoresce red in light of wavelength around 400 nm They are widely distributed throughout the animal and plant kingdom Protoporphyrin IX occurs in the pigmented eggshells of many species of birds while uroporphyrin is found in the shells of molluscs However, their most important role is when complexed to metals to form metalloporphyrins, which are essential for all biological oxidation reactions Haem is the iron complex of protoporphyrin The rodent Harderian gland is remarkable in its ability to synthesise porphyrins, which in some species exceeds that of the liver
TL;DR: The data demonstrate that octa-alkylporphyrins can be productively used as models for protoporphyrin IX in studies of heme proteins with MCD spectroscopy.
TL;DR: This spectrofluorometric method designed for the determination of protoporphyrin IX, esterified and nonesterified Mg-protoporphyr in pool, and protochlorophyllide is far superior to available spectrophotometric methods and estimates as low as 1 nM concentration of plant pigments.
TL;DR: In this paper, the molecular properties of phenopylate (2,4-dichlorophenyl 1-pyrrolidine carborylate) and 13 of its O-phenyl pyrrolidino-and piperidinocarbamate analogues were correlated with their capacity to inhibit protoporphyrinogen oxidase (Protor), to cause accumulation of protopmorphyrin IX, and to cause herbicidal injury.
Abstract: The molecular properties of phenopylate (2,4-dichlorophenyl 1-pyrrolidinecarborylate) and 13 of its O-phenyl pyrrolidino- and piperidinocarbamate analogues were correlated with their capacity to inhibit protoporphyrinogen oxidase (Protor), to cause accumulation of protoporphyrin IX, and to cause herbicidal injury. All three biological properties correlated well with the van der Waalsvolume, electrophilic superdelocalizability, and energy of the lowest unoccupied molecular orbital. The relationships between biological activities and log P were curvilinear. The activity was mainly centered on the phenyl ring
TL;DR: This chapter discusses the mechanistic features of P-450 reactions by comparing enzymic reactions with those of model porphyrin systems by demonstrating for the first time the participation of P -450 in the C-12 hydroxylation of steroids catalyzed by adrenal cortex microsomes.
Abstract: Publisher Summary This chapter discusses the mechanistic features of P-450 reactions by comparing enzymic reactions with those of model porphyrin systems. Model porphyrin systems have allowed the complete dissection of the proposed mechanism of oxygen activation and transfer by P-450. The P-450 enzyme comprises a unique class of hemoprotein that has protoporphyrin IX at the active site as a prothetic group, an unusual cysteine thiolate ligand to the heme iron, and a characteristic absorption band at 450 nm. The physiological function of P-450 is the oxidative metabolism of foreign compounds (such as drugs and cancer reagents) and steroids in the liver, lung, and placenta, via an oxygen transfer mechanism. Estabrook and co-workers demonstrated for the first time the participation of P-450 in the C-12 hydroxylation of steroids catalyzed by adrenal cortex microsomes. The P-450 reaction cycle begins with binding of the substrate at the active site. This process can be observed spectroscopically as the incorporation of the substrate eliminates the iron-coordinated water molecule from the active site causing spin-state changes in some cases.
TL;DR: The hypothesis that the sensitivity of the visA mutants to light is caused by the abnormal accumulation of Proto IX, a substrate of ferrochelatase, as the result of a genetic defect in the gene for ferroChelatase is confirmed.
TL;DR: The results indicate that the site at which DPEs inhibit protoporphyrinogen IX oxidase shows chiral discrimination and provide further evidence for the link between inhibition of this enzyme, protoprophyrin IX accumulation, and the phytotoxicity of DPE herbicides.
Abstract: The nitrodiphenyl ether herbicide 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitroacetophenone oxime-O-(acetic acid, methyl ester) (DPEI) induced an abnormal accumulation of protoporphyrin IX in darkness in the green alga Chlamydomonas reinhardtii, as determined by high-performance liquid chromatography and spectrofluorimetry. It also inhibited the increase in cell density of the alga in light-grown cultures with an I50 (concentration required to decrease cell density increase to 50% of the noninhibited control value) of 0.16 μm. The relative ability of four peroxidizing diphenyl ether herbicides to cause tetrapyrrole accumulation in C. reinhardtii correlated qualitatively with their ability to inhibit the increase in cell density in light-grown cultures. The purified S(−) enantiomer of the optically active phthalide DPE 5-[2-chloro-4-(trifluoromethyl)phenoxy]-3-methylphthalide (DPEIII), which has greater herbicidal activity than the R(+) isomer, induces a 4- to 5-fold greater tetrapyrrole accumulation than the R(+) isomer. The I50 for inhibition of increase in cell density in light-grown cultures of C. reinhardtii by the S(−) isomer (0.019 μm) is less than 25% of that for the R(+) isomer. DPEIII inhibits protoporphyrinogen IX oxidase activity in pea (Pisum sativum) etioplast lysates, with the S(−) enantiomer showing considerably greater potency than the R(+) isomer and the racemic mixture showing a potency intermediate between the two. The results indicate that the site at which DPEs inhibit protoporphyrinogen IX oxidase shows chiral discrimination and provide further evidence for the link between inhibition of this enzyme, protoporphyrin IX accumulation, and the phytotoxicity of DPE herbicides.
Journal Article•
TL;DR: An organelle-free assay for Mg-chelatase has been developed from lysed pea chloroplasts, and has been refined by removing the bulk of the thylakoid membranes.
TL;DR: In this paper, a series of peroxidative cyclic imides were assayed with respect to degradation of chlorophyll (bleaching), light-induced ethane formation, growth inhibition, and protoporphyrin IX (proto IX) levels.
TL;DR: Most or all of the herbicidal damage caused by these compounds is due to inhibition of Protox, as indicated by correlations found between Protox I50 values and herbicidal activity of the more active of the compounds.
Abstract: Phenopylate1 (2, 4-dichlorophenyl 1-pyrrolidinecarboxylate) and 13 of its O-phenyl pyrrolidino- and piperidino-carbamate analogues were tested for their capacity to inhibit protoporphyrinogen oxidase (Protox), to cause accumulation of protoporphyrin IX (Proto IX), and to cause herbicidal injury All 14 compounds inhibited Protox of barley etioplast preparations The I50 values ranged from 21 nM to 4 mM Highly significant correlations were found between Protox I50 values and herbicidal activity of the more active of the compounds on greenhouse-grown weeds (pitted morningglory, barnyardgrass, prickly sida, and velvetleaf), pre- and/or post-emergence, and on cucumber cotyledon discs or barley leaf sections in cellular leakage bioassays Proto IX accumulation in barley leaf sections treated with any of the 14 compounds correlated well with both the I50 values for Protox inhibition and with herbicidal damage to the tissue sections These data indicate most or all of the herbicidal damage caused by these compounds is due to inhibition of Protox
TL;DR: In this paper, the authors found that acifluenmethyl (AFM) stimulation of Proto IX (Proto IX) accumulation in Lemna pausicostata Hegelm. 6746 plants in the light and in the dark was associated with increased photobleaching and reduced porphyrin synthesis.
Abstract: In Lemna pausicostata Hegelm. 6746, light is required for sufficient acifluorfenmethyl (AFM) stimulation of protoporphyrin IX (Proto IX) accumulation to cause significant herbicidal action. In darkness, AFM causes Proto IX levels to increase for about 2 h, after which Proto IX content is stable at levels significantly lower than those accumulated in light. In darkness, sucrose cannot increase levels of AFM-induced Proto IX. However, addition of δ-aminolevulinic acid (ALA) increases Proto IX levels in AFM-treated plants in darkness, demonstrating that the herbicide blocks the porphyrin pathway in darkness as it does in the light. Thus, Proto IX accumulation in darkness appears to be limited by ALA availability. This is supported by the finding that dioxoheptanoic acid caused more ALA to accumulate in light than in darkness. Heme is a feedback inhibitor of ALA synthesis, and heme synthesis is inhibited by AFM. However, total extractable heme levels were reduced by AFM by about the same amount in both light and darkness. Exogenously supplied hemin reduced AFM-caused Proto IX accumulation and herbicidal damage in the light and also reduced Proto IX accumulation caused by AFM or AFM plus ALA in darkness. AFM-stimulated Proto IX accumulation was inversely proportional to the log of the photon flux density between 5 and 500 μmol in m−2 s−1. Reduced effects of higher photon fluxes on AFM-stimulated Proto IX accumulation are probably due to both increased photobleaching of Proto IX and reduced porphyrin synthesis because of herbicidal damage. AFM-stimulated Proto IX accumulation in darkness could not be demonstrated to be under phytochrome control, but it appeared to be under the negative influence of protochlorophyllide levels.
Journal Article•
TL;DR: Detached, etiolated cotyledons from the chlorophyll-deficient ch4 mutant of sweetclover failed to accumulate elevated levels of protochlorophyllide, magnesium protoporphyrin IX or protoporalin IX when incubated in the dark with 1 mM δ-aminolevulinic acid.
TL;DR: In this article, a laboratory robot was used to perform fecal porphyrin analysis on 20 healthy volunteers, and the results showed that the sample contained 7.1 nmol/g dry wt, 3.0 (SD 0.4), and 4.4 (SD 4.3), respectively.
Abstract: Unpleasant specimens, sensitive analytes, and a lengthy chromatographic procedure were the main reasons we implemented fecal porphyrin analysis with a laboratory robot. We describe the system in detail and compare it with the same technique performed manually. The day-to-day variation of assays of standards was lower with the robot than with the manual operation: 8% (CV) for coproporphyrin I and 11% for protoporphyrin IX. We repeatedly analyzed a specimen from a healthy volunteer and determined that the specimen contained (in nmol/g dry wt) 7.1 (SD 0.7) for coproporphyrin I, 3.0 (SD 0.4) for coproporphyrin III, and 44.4 (SD 4.3) for protoporphyrin IX. Upper reference limits as measured in 20 healthy volunteers were 20 nmol/g dry wt for coproporphyrin I, 12 nmol/g for coproporphyrin III, and 80 nmol/g for protoporphyrin IX. We also present characteristic chromatograms for samples from various different porphyrias that exhibit abnormal fecal porphyrin excretion. Calculations of return on investment show that the robot, working at full capacity, is a profitable tool.
TL;DR: In this article, the lifetime of the excited singlet state of the protoporphyrin IX was found to decrease from 13.7 ns to 6.2 ns after polymerization.
Abstract: The macromolecular bound protoporphyrin IX and its metal complexes, poly-(protoporphyrin-co-acrylamide), cobalt(II) [poly(protoporphyrin-co-acrylamide)], zinc-(II)[poly(protoporphyrin-co-acrylamide)], and manganese(III) [poly(protoporphyrin-co-acrylamide)] chloride were synthesized. The absorption and emission spectra have been obtained for the macromolecular porphyrins. The lifetime of the excited singlet state of the protoporphyrin IX was found to decrease from 13.7 to 6.2 ns after polymerization. The cyclic voltammograms of polymeric protoporphyrin coated electrodes have been obtained.
TL;DR: It was shown that oxyfluorfen-induced protoporphyrin IX accumulation was increased by light in all plant species, indicating that light acts as an enhancer of the accumulation in intact plants.
TL;DR: Porphyrins (3)-(5) were found to localize in mitochondria, and this is proposed to account for their greater photosensitivity effectiveness when compared with hematoporphyrin derivative.
Abstract: A series of pure porphyrins (3)-(11) derived from amidation of the carboxylic acid groups of protoporphyrin IX was synthesized in high yield by using 1,11-carbonyldiimidazole as the coupling reagent. Preliminary biological evaluation of these porphyrins revealed that (3) and (10) localize in tumour tissue in concentrations 20 times greater than the surrounding normal tissue. Porphyrins (3)-(5) were found to localize in mitochondria, and this is proposed to account for their greater photosensitivity effectiveness when compared with hematoporphyrin derivative. The extent of binding of the basic porphyrins (3) and (4) to DNA was ascertained by absorbance titrations with DNA, and binding constants were found to be (1.0-1.5) × 106 dm3 mol-1 with six base pairs occluded for both compounds.
01 Jan 1992
TL;DR: To elucidate the chl biosynthetic pathways and to monitor the amount of over-accumulated porphyrins to induce photodynamic damage to the plants, it is essential to correct the fluorescence amplitude of the compound to be quantified for the contribution due to other fluorescing compounds at the measured wavelength.
Abstract: The chlorophyll (chl) molecules are synthesized from 5 aminolevulinic acid (ALA) via various intermediates. It is already demonstrated that chl biosynthesis takes place via monovinyl and divinyl monocarboxylic routes (2,4–6). To elucidate the chl biosynthetic pathways and to monitor the amount of over-accumulated porphyrins to induce photodynamic damage to the plants (1,3), the various pools of intermediates of chl biosynthetic pathway like protoporphyrin IX (Proto IX), mg-protoporphyrin monoester (MPE) or protochlorophyllide (Pchlide) etc. need to be quantified (4). In small amount of tissues and especially in isolated etioplasts or chloroplasts the pools of above intermediates are too small to be estimated spectrophotometrically. As Proto IX, MPE and Pchlide fluoresce, and spectrofluorometry is a very sensitive tool, the fluorescence of these compounds can be measured for their quantification. However, as these components especially Proto IX, Pchlide and Chlide are having overlapping fluorescence spectra, it would be incorrect to quantify the above components from their mixtures by measuring fluorescence amplitudes at their respective peaks. Therefore it is essential to correct the fluorescence amplitude of the compound to be quantified (say Proto IX) for the contribution due to other fluorescing compounds (say Pchlide and Chlide) at the measured wavelength.