INVITRO METABOLISM OF POSSIBLE ECDYSONE PRECURSORS BY THE PROTHORACIC GLANDS OF THE TOBACCO HORNWORM, MANDUCA-SEXTA

3β,14α-Dihydroxy-5α-cholest-7-en-6-one (5α-ketodiol) (1) is metabolized by the prothoracic glands to 2,22-dideoxy-5α-ecdysone (4) and 2-deoxy-5α-ecdysone (3) but not to ecdysone (5) or any other 5β-metabolites. Similarly, 3β,5α,14α-trihydroxy-cholest-7-en-6-one (5α-ketotriol) (8) is hydroxylated at C-22 and C-25 (9, 10) of the side chain. However, 3β,14α-dihydroxy-cholesta-4,7-diene-6-one (ketodienediol) (11) is not metabolized. The absence of 2β-hydroxymetabolites for substrates (1) and (8) implies that hydroxylation at C-2 can occur only when the A-B rings are cis fused (5β-configuration). By contrast, the enzyme complexes that introduce hydroxyls at C-22 and C-25 do not exhibit a preference for cis over trans fusion and apparently cannot recognize the planar A-B ring configuration. © 1979 Holden-Day Inc.