ECDYSTEROID BIOSYNTHESIS IN MOLTING GLANDS OF THE CRAYFISH ORCONECTES-LIMOSUS - EVIDENCE FOR THE SYNTHESIS OF 3-DEHYDROECDYSONE BY INVITRO SYNTHESIS AND CONVERSION STUDIES

Ecdysteroids secreted in vitro by the Y-organs of Orconectes limosus were measured by radioimmunoassay after HPLC-separation of culture media. Ecdysone and 3-dehydroecdysone were found as secretory products. Metabolic studies with [H-3]ecdysone and [H-3]3-dehydroecdysone showed that Y-organs are not able to convert 3DE into E or vice versa. The putative precursors 5beta-ketodiol and 5beta-diketol (''3-oxoketodiol'') were both converted by Y-organs. [H-3]5beta-ketodiol was converted into E. [H-3]5beta-diketol was converted into 3DE and E. Ketodiol was also observed as a conversion product of 5beta-diketol. Our data suggest, that in Orconectes 5beta-diketol is a good candidate for an intermediate in the ecdysteroid biosynthetic pathway and that there is a branching of the pathway leading to 3DE as well as to E, due to the activity of a 3-oxoecdysteroid-3beta-reductase specific for less hydroxylated compounds.