Cytochrome P-450-dependent oxidation of progesterone, testosterone, and ecdysone in the spiny lobster, Panulirus argus

Abstract

Experiments were performed to determine the ability of the cytochrome P-450 present in hepatopancreas microsomes from the spiny lobster, Panulirus argus, to catalyze oxidation of progesterone, testosterone, and ecdysone. Preparations of hepatopancreas microsomes fortified with NADPH cytochrome P-450 reductase from pig liver efficiently catalyzed NADPH-dependent 16α- and 6β-hydroxylation of progesterone and testosterone, and 21-hydroxylation of progesterone. These products were also found if NADPH and NADPH cytochrome P-450 reductase were replaced by cumene hydroperoxide. Cytochrome P-450 purified from hepatopancreas microsomes catalyzed NADPH- and reductase-dependent 16α-hydroxylation of progesterone and testosterone 10 times more rapidly than the original microsomal preparation. While ecdysone was not a substrate for the hepatopancreas microsomal cytochrome P-450, low ecdysone 20-monooxygenase activity was found in hepatopancreas mitochondria. Further studies showed that homogenates of green gland, ovaries, and testes had higher ecdysone monooxygenase activities than hepatopancreas, and that the activity in green gland was localized in mitochondria.