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INACTIVATION OF CITRIC ACID CYCLE ENZYMES AS A RESULT OF PHOTODYNAMIC SENSITIZATION BY MITOCHONDRIAL INNER MEMBRANE
Author(s) -
Jung Jin,
Kim YongJae
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb01818.x
Subject(s) - biochemistry , enzyme , citric acid cycle , isocitrate dehydrogenase , inner mitochondrial membrane , chemistry , mitochondrion , citrate synthase , aconitase , citric acid , nad+ kinase , biology
— Exposure to blue light of mitochondria under aerobic conditions resulted in inactivation of the regulatory enzymes of the citric acid cycle (CAC) contained in the mitochondrial matrix, except citrate synthase. When “soluble mitochondrial protein” was exposed to blue light under aerobic conditions, no significant loss of activity was observed for any CAC enzymes. However, the inclusion of submitochondria particles (SMP) in the photolysis system resulted in a substantial inactivation of the CAC enzymes. Of the CAC enzymes, NAD+‐specific isocitrate dehydrogenase (ICDH) appeared to be most susceptible to the membrane dependent‐photoinactivation. Imidazole protected the CAC enzymes against inactivation. In contrast, superoxide dismutase failed to protect them, except α‐ketoglutarate dehydrogenase. The photoinhibition of ICDH activity was drastically depressed in the presence of SMP whose Fe‐S centers were destroyed by the mersalyl acid treatment. The results obtained in this study suggest that the photoinactivation of the CAC enzymes in situ is mediated mainly by singlet oxygen, which is photoproduced primarily by the Fe‐S centers of mitochondrial membranes.