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 w ere measured by radioimmunoassay after HPLC-separation of culture medi a. Ecdysone and 3-dehydroecdysone were found as secretory products. Me tabolic studies with [H-3]ecdysone and [H-3]3-dehydroecdysone showed t hat Y-organs are not able to convert 3DE into E or vice versa. The put ative precursors 5beta-ketodiol and 5beta-diketol (''3-oxoketodiol'') were both converted by Y-organs. [H-3]5beta-ketodiol was converted int o E. [H-3]5beta-diketol was converted into 3DE and E. Ketodiol was als o observed as a conversion product of 5beta-diketol. Our data suggest, that in Orconectes 5beta-diketol is a good candidate for an intermedi ate in the ecdysteroid biosynthetic pathway and that there is a branch ing 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.