PRESENCE OF AN NAD(P)H DEHYDROGENASE AND A B-TYPE CYTOCHROME DIFFERENT FROM THE RESPIRATORY-CHAIN IN SUBMITOCHONDRIAL PARTICLES FROM HUMAN PLACENTA

Placental submitochondrial particles can synthesize progesterone. Both , progesterone synthesis and oxygen consumption were stimulated in the presence of succinate, NADH, or NADPH. NADPH reduced the cytochromes of the respiratory chain in a similar way as NADH. NADPH oxidation was not achieved by NADH-DH from the respiratory chain, and the presence of an NAD(P)H-DH is suggested. Submitochondrial particles contain at l east two b-type cytochromes, one inhibited by antimycin when the elect ron donor is succinate, whereas the other is less sensitive to antimyc in in the presence of pyridine nucleotides. The results suggest a conn ection between the respiratory chain and cytochrome P450, through an N AD(P)H-DH and a b-type cytochrome, both different from the respiratory chain.