Showing papers on "Protoporphyrin IX published in 1978"
TL;DR: Preferential rupture of the outer membrane of mitochondria from rat liver releases coproporphyrinogen oxidase in parallel with components of the intermembrane space to allow haem synthesis to be completed.
Abstract: Preferential rupture of the outer membrane of mitochondria from rat liver releases coproporphyrinogen oxidase in parallel with components of the intermembrane space. Coproporphyrinogen III enters the mitochondrion through the freely-permeable outer membrane. Either protoporphyrinogen IX or protoporphyrin IX must then cross the inner membrane before haem synthesis can be completed.
80 citations
TL;DR: Mixed-substrate experiments indicate that this reaction is catalysed by coproporphyrinogen oxidase and that the Km for this substrate is 29 micron, and it is suggested that the ratio of the concentration of pentacarboxylate porphyr inogen III to copropoiryringen III in the hepatocyte determines the relative rates of formation of dehydroisocoproporphinogen and protoporphyrInogen IX.
Abstract: [14C2]Coproporphyrin III, 14C-labelled in the carboxyl carbon atoms of the 2- and 4-propionate substituents, was prepared by stepwise modification of the vinyl groups of protoporphyrin IX. The corresponding porphyrinogen was used as substrate in a specific sensitive assay for coproporphyrinogen oxidase (EC 1.3.3.3) in which the rate of production of 14CO2 is measured. With this method, the Km of the enzyme from rat liver for coproporphyrinogen III is 1.2 micron. Coproporphyrin III is a competitive inhibitor of the enzyme (Ki 7.6 micron). Apparent Km values for other substrates were measured by a mixed-substrate method: that for coproporphyrinogen IV is 0.9 micron and that for harderoporphyrinogen 1.6 micron. Rat liver mitochondria convert pentacarboxylate porphyrinogen III into dehydroisocoproporphyrinogen at a rate similar to that for the formation of protoporphyrinogen IX from coproporphyrinogen III. Mixed-substrate experiments indicate that this reaction is catalysed by coproporphyrinogen oxidase and that the Km for this substrate is 29 micron. It is suggested that the ratio of the concentration of pentacarboxylate porphyrinogen III to coproporphyrinogen III in the hepatocyte determines the relative rates of formation of dehydroisocoproporphyrinogen and protoporphyrinogen IX.
55 citations
TL;DR: Findings further support the views that heme oxygenase may have a heme-binding crevice similar to those of myoglobin and hemoglobin and that reduction of heme is the prerequisite for the oxidative degradation of he me in the hemeoxyase reaction.
45 citations
TL;DR: At ionic strengths near physiological the authors can find no evidence of binding of haemoglobin to spectrin, as judged by sedimentation velocity, and it appears that reported interactions of this nature represent only non-specific binding at low ionic strength.
Abstract: Haemin and protoporphyrin IX, but not bilirubin, are extensively bound by human spectrin. The absorption spectrum of the bound haemin is indicative of coordination of the iron by nitrogenous ligands in the protein. The protoporphyrin IX generates difference spectra on binding, which change with ligand:protein ratio, showing the existence of at least two structurally distinct types of site. The binding of both ligands is complex, and may be cooperative. Binding isotherms, based on spectrophotometric titrations, are given. Haemin and protoporphyrin IX also bind strongly to erythrocyte ghosts. At ionic strengths near physiological we can find no evidence of binding of haemoglobin to spectrin, as judged by sedimentation velocity, and it appears that reported interactions of this nature represent only non-specific binding at low ionic strength.
38 citations
35 citations
TL;DR: Four mutants of maize defective in chlorophyll biosynthesis have been analyzed with regard to the sites of their lesions and their effects on chloroplast development and the etioplasts of these mutants contain noncrystalline bodies.
Abstract: Four mutants of maize (Zea mays L.) defective in chlorophyll biosynthesis have been analyzed with regard to the sites of their lesions and their effects on chloroplast development. Two yellow mutants, which accumulate no detectable porphyrin precursors when grown in darkness, are defective in the conversion of protoporphyrin IX to magnesium protoporphyrin. Etioplasts of these mutants may develop elaborate lamellar membrane systems, but prolamellar bodies are never observed. Two mutants, which are necrotic when grown under illumination, develop normal (non-necrotic) leaf tissue in the dark and accumulate a small amount of magnesium protoporphyrin monomethyl ester, corresponding approximately to the amount of protochlorophyllide accumulated by normal plants. The etioplasts of these mutants contain noncrystalline bodies. The implications of these observations with respect to chloroplast development are discussed.
33 citations
TL;DR: A dominant modifier gene, Orom, which allows oro seedlings to bypass their lesion, and several mutants of maize defective in chlorophyll synthesis are analysed.
Abstract: Several mutants of maize defective in chlorophyll synthesis are analysed. By feeding shoots of dark-grown seedlings δ-aminolevulinic acid, the regulatory step in chlorophyll biosynthesis is bypassed and chlorophyll precursors accumulate. In normal plants this results in a buildup of protoporphyrin IX and protochlorophyllide, while mutants accumulate precursors, depending on the site of the mutant-induced lesion. Mutants at three loci, l*-Blandy4, 113, and oy, are defective in conversion of protoporphyrin IX to Mg-protoporphyrin. Mutants at the oro and oro2 loci are defective in conversion of Mg-protoporphyrin monomethyl ester to protochlorophyllide. A dominant modifier gene, Orom, which allows oro seedlings to bypass their lesion is also described.
30 citations
20 citations
TL;DR: This review considers the stages and enzymes between coproporphyrinogen-III and protopomorphyrin-IX to determine the carrier and removal status of these substances.
18 citations
16 citations
TL;DR: In this article, it was shown that the dihydro and monohydrated derivatives of protoporphyrin IX dimethyl ester can be synthesized by partial dehydration and reduction.
Abstract: Rational syntheses of the dihydro [(1d), (1e)] and monohydrated [(1b), (1c)] derivatives of protoporphyrin IX dimethyl ester have been completed. It has also been shown that the latter isomers [(1b), (1c)] can be obtained either from haematoporphyrin IX dimethyl ester (1a) by partial dehydration, or from diacetyldeuteroporphyrin IX dimethyl ester (1f) by partial reduction followed by dehydration and reduction.
TL;DR: The level of some enzymatic activities in red blood cells before and after photohemolysis induced by protoporphyrin IX was studied and a 30% decrease in catalase activity was found both in normal erythrocytes and in patients affected by favism.
Abstract: The level of some enzymatic activities in red blood cells before and after photohemolysis induced by protoporphyrin IX was studied. A 30% decrease in catalase activity was found both in normal erythrocytes and those from patients affected by favism. Other proteins though present in larger amounts inside the erythrocytes are not affected by the photohemolytic process.
01 Jan 1978
TL;DR: In this article, flash photolysis of aqueous solutions of protoporphyrin IX at pH values below 2 results in strong triplet state absorptions while at any higher pH, including physiologically relevant values, no triplet states formation can be detected.
Abstract: Flash photolysis of aqueous solutions of protoporphyrin IX at pH values below 2 results in strong triplet state absorptions while at any higher pH, including physiologically relevant values, no triplet state formation can be detected.
TL;DR: Bovine blood is suitable as an erythrocyte protoporphyrin control material for laboratories using acid extraction procedures, but not for the proficiency testing of laboratories using hematofluorometers.
Abstract: Bovine blood is used frequently as control material in interlaboratory comparisons for blood-lead analysis, but an erythrocyte protoporphyrin control material is needed. We present data on the rate of changes in blood lead and erythrocyte protoporphyrin in steers fed lead acetate. We also show, by comparison of fluorescence spectra with those of known compounds, that most of the porphyrin in lead-burdened steers probably exists as free protoporphyrin IX along with some zinc-complexed protoporphyrin IX. Bovine blood is suitable as an erythrocyte protoporphyrin control material for laboratories using acid extraction procedures, but not for the proficiency testing of laboratories using hematofluorometers.
TL;DR: Soybean apoleghemoglobin a was irradiated with visible light in the presence of different sensitizers to probe the heme environment of the protein and lost tryptophan-128 in addition to the two histidines.
Abstract: Soybean apoleghemoglobin a was irradiated with visible light in the presence of different sensitizers to probe the heme environment of the protein. With protoporphyrin IX as sensitizer, specific photooxidation of histidine-92 and histidine-61 occurred. Irradiation of oxyleghemolglobin and cyanleghemoglobin resulted in photooxidation of histidine-92, while addition of methylene blue caused both histidine-92 and histidine-61 to be oxidized. Apoleghemoglobin, irradiated in the presence of rose bengal or methylene blue, lost tryptophan-128 in addition to the two histidines.
TL;DR: Treatment of protoporphyrin-IX dimethyl ester with picryl azide affords an equimolar mixture of chlorocruoro- and isochlorocruero-porphyrin dimethyl isters as mentioned in this paper.
Abstract: Treatment of protoporphyrin-IX dimethyl ester with picryl azide affords an equimolar mixture of chlorocruoro- and isochlorocruoro-porphyrin dimethyl esters.
Journal Article•
TL;DR: In this paper, it was shown that the dihydro and monohydrated derivatives of protoporphyrin IX dimethyl ester can be synthesized by partial dehydration and reduction.
Abstract: Rational syntheses of the dihydro [(1d), (1e)] and monohydrated [(1b), (1c)] derivatives of protoporphyrin IX dimethyl ester have been completed. It has also been shown that the latter isomers [(1b), (1c)] can be obtained either from haematoporphyrin IX dimethyl ester (1a) by partial dehydration, or from diacetyldeuteroporphyrin IX dimethyl ester (1f) by partial reduction followed by dehydration and reduction.