Effect of xanthurenic acid on P-450-dependent biotransformation by molting glands in vitro.

Incubation of molting glands from the crayfish Procambarus clarkii (Y-organ) and the silkworm Bombyx mori (prothoracic gland) with 23,24-[H]-2-deoxyecdysone resulted in the production of deutero-ecdysone; this biotransformation was inhibited in the presence of xanthurenic acid. When the experiments were performed under anO atmosphere, theO atom was introduced into ecdysone, as confirmed by mass spectrometry. We therefore suggest that xanthurenic acid inhibits P-450-dependent hydroxylation of 2-deoxyecdysone. However, deutero-2-deoxyecdysone was not converted to 3-dehydroecdysone when using Y-organs in vitro, although it is a major product. We therefore conclude that the biosynthetic pathway of ecdysteroids in P. clarkii branches at an early step. [ABSTRACT FROM AUTHOR]