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Protoporphyrin IX

About: Protoporphyrin IX is a research topic. Over the lifetime, 2250 publications have been published within this topic receiving 65544 citations. The topic is also known as: PpIX.


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Journal ArticleDOI
TL;DR: An abnormal porphyrin, tentatively identified as an NN-bridged benzyne-protoporphyr in IX adduct, appears to be formed by the addition of catalytically generated benzynes to prosthetic haem.
Abstract: Destruction of hepatic cytochrome P-450 during catalytic processing of 1-amino-benzotriazole is accompanied by an equal loss of microsomal haem but not by loss of cytochrome b5, or stimulation of lipid peroxidation. An abnormal porphyrin, tentatively identified as an NN-bridged benzyne-protoporphyrin IX adduct, appears to be formed by the addition of catalytically generated benzyne to prosthetic haem.

200 citations

Journal ArticleDOI
TL;DR: Observations suggest that functional atABC1 is required for the transport and correct distribution of protoporphyrin IX, which may act as a light-specific signaling factor involved in coordinating intercompartmental communication between plastids and the nucleus.
Abstract: Plants perceive light via specialized photoreceptors of which the phytochromes (phyA-E), absorbing far-red (FR) and red light (R) are best understood. Several nuclear and cytoplasmic proteins have been characterized whose deficiencies lead to changes in light-dependent morphological responses and gene expression. However, no plastid protein has yet been identified to play a role in phytochrome signal transduction. We have isolated a new Arabidopsis mutant, laf (long after FR) 6, with reduced responsiveness preferentially toward continuous FR light. The disrupted gene in laf6 encodes a novel plant ATP-binding-cassette (atABC1) protein of 557 amino acids with high homology to ABC-like proteins from lower eukaryotes. In contrast to lower eukaryotic ABCs, however, atABC1 contains an N-terminal transit peptide, which targets it to chloroplasts. atABC1 deficiency in laf6 results in an accumulation of the chlorophyll precursor protoporphyrin IX and in attenuation of FR-regulated gene expression. The long hypocotyl phenotype of laf6 and the accumulation of protoporphyrin IX in the mutant can be recapitulated by treating wild-type (WT) seedlings with flumioxazin, a protoporphyrinogen IX oxidase (PPO) inhibitor. Moreover, protoporphyrin IX accumulation in flumioxazin-treated WT seedlings can be reduced by overexpression of atABC1. Consistent with the notion that ABC proteins are involved in transport, these observations suggest that functional atABC1 is required for the transport and correct distribution of protoporphyrin IX, which may act as a light-specific signaling factor involved in coordinating intercompartmental communication between plastids and the nucleus.

200 citations

Journal ArticleDOI
TL;DR: Using this system, it is found possible to obtain good emission and excitation spectra of the material responsible for the weak red fluorescence that characterizes normal mouse skin, and to follow the biosynthesis and subsequent clearance of protoporphyrin IX in the skin of non‐anesthetized mice that had been given various doses of the porphyrIn precursor 5‐aminolevulinic acid.
Abstract: An intensified photodiode array forms the heart of a sensitive spectrophotofluorometry system that permits the rapid and non-invasive determination of fluorescence emission spectra in the skin of living, non-anesthetized animals. Using this system, we found it possible to obtain good emission and excitation spectra of the material responsible for the weak red fluorescence that characterizes normal mouse skin, and to follow the biosynthesis and subsequent clearance of protoporphyrin IX in the skin of non-anesthetized mice that had been given various doses of the porphyrin precursor 5-aminolevulinic acid.

194 citations

Journal ArticleDOI
TL;DR: It is demonstrated that heme oxygenase 2 is localized to glomus cells in the cat and rat carotid bodies, and results suggest that glomUS cells are capable of synthesizing CO and endogenous CO appears to be a physiologic regulator of carotids body sensory activity.
Abstract: Carbon monoxide (CO), produced endogenously by heme oxygenase, has been implicated as a neuronal messenger. Carotid bodies are sensory organs that regulate ventilation by responding to alterations of blood oxygen, CO2, and pH. Changes in blood gases are sensed by glomus cells in the carotid body that synapse on afferent terminals of the carotid sinus nerve that projects to respiratory-related neurons in the brainstem. Using immunocytochemistry, we demonstrate that heme oxygenase 2 is localized to glomus cells in the cat and rat carotid bodies. Physiological studies show that zinc protoporphyrin IX, a potent heme oxygenase inhibitor, markedly increases carotid body sensory activity, while copper protoporphyrin IX, which does not inhibit the enzyme, is inactive. Exogenous CO reverses the stimulatory effects of zinc protoporphyrin IX. These results suggest that glomus cells are capable of synthesizing CO and endogenous CO appears to be a physiologic regulator of carotid body sensory activity.

192 citations

Journal ArticleDOI
TL;DR: The results presented here implicate ABCG2 as a possible cause for cellular resistance to photodynamic therapy.
Abstract: In photodynamic therapy (PDT), a tumor-selective photosensitizer is administered followed by activation of the photosensitizer by exposure to a light source of a given wavelength. This, in turn, generates reactive oxygen species that induce cellular apoptosis and necrosis in tumor tissue. Based on our earlier finding that the photosensitizer pheophorbide a is an ABCG2 substrate, we explored the ability of ABCG2 to transport photosensitizers with a structure similar to that of pheophorbide a. ABCG2-overexpressing NCI-H1650 MX50 bronchoalveolar carcinoma cells were found to have reduced intracellular accumulation of pyropheophorbide a methyl ester and chlorin e6 compared to parental cells as measured by flow cytometry. The ABCG2 inhibitor fumitremorgin C was found to abrogate ABCG2-mediated transport. Intracellular fluorescence of hematoporphyrin IX, meso-tetra(3-hydroxyphenyl)porphyrin, and meso-tetra(3-hydroxyphenyl)chlorin was not substantially affected by ABCG2. ABCG2-overexpressing cells also displayed decreased intracellular fluorescence of protoporphyrin IX generated by exogenous application of 5-aminolevulinic acid. Mutations at amino acid 482 in the ABCG2 protein known to affect substrate specificity were not found to impact transport of the photosensitizers. In cytotoxicity assays, ABCG2-transfected HEK-293 cells were 11-fold, 30-fold, 4-fold, and >7-fold resistant to PDT with pheophorbide a, pyropheophorbide a methyl ester, chlorin e6, and 5-aminolevulinic acid, respectively. ABCG2-transfected cells were not resistant to PDT with meso-tetra(3-hydroxyphenyl) chlorin. Neither multidrug resistance-associated protein 1 expression nor P-glycoprotein expression appreciably decreased the intracellular fluorescence of any of the photosensitizers examined as determined by flow cytometry. The results presented here implicate ABCG2 as a possible cause for cellular resistance to photodynamic therapy.

187 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202383
2022132
202157
202061
201958
201858