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Direct Oxidation of NADPH by Submitochondrial Particles from Saccharomyces cerevisiae

1980; Wiley; Volume: 107; Issue: 2 Linguagem: Inglês

10.1111/j.1432-1033.1980.tb06056.x

1432-1033

Fereydoun H. S. DJAVADI, Mahnaz Moradi, Lisa Djavadi‐Ohaniance,

Analytical chemistry methods development

It has been accepted that in Saccharomyces cerevisiae submitochondrial particles do not oxidize the NADPH and that the NADPH:cytochrome c reductase is not a mitochondrial enzyme but rather a microsomal one. The present study provides clear evidence that in S. cerevisiae a direct oxidation of NADPH occurs through the mitochondrial electron transport system. The following results wee obtained: submitochondrial particles from S. cerevisiae are capable of oxidizing NADPH with a relatively high rate. The oxidation of NADPH is sensitive to antimycin A and NaN3 but insensitive to rotenone as is known for NADPH oxidation. Also NADPH:cytochrome c reductase activity is inhibited by antimycin A. NADPH-induced reduction of cytochromes b, c + c1, and aa3 is as fast as NADPH-induced reduction. Cytochromes are reduced to the same extent with either NADH or NADPH. The changes of the ratio of NADH/NADPH oxidation rate and the ratio of NADH K3Fe(CN)6/NADPH-K3Fe(CN)6 reductase activities at various phases of growth suggest that two distinct pyridine nucleotide dehydrogenases could be responsible for NADH and NADPH oxidation. This problem remains to be elucidated.