The specificity of juvenile hormone esterase revisited

Juvenile hormone esterase (JHE) catalyses the transesterification of juvenile hormones (JH) in the presence of appropriate alcohols to yield ethyl, propyl or butyl JH esters. Using baculovirus-expressed, recombinant Heliothis virescens JHE or hemolymph from several species, we have produced 200-300 mu g of JH III ethyl, n-propyl and n-butyl esters from 1.0 mg JH III incubated in 30% (v/v) ethanol, 10% l-propanol or 5% 1-butanol. Alternatively, highly pure JH ethyl esters were chemically synthesized by treating JH acids with diazoethane. Structures were verified by nuclear magnetic resonance (NMR) and/or gas chromatography-mass spectrometry (GC-MS). The hemolymph of Manduca sexta, Tenebrio molitor, Trichoplusia ni, or Schistocerca americana, or recombinant H. virescens JHE all exhibit the same trend in JH ester hydrolysis rate: methyl = ethyl>n-propyl>>n-butyl. In contrast, Blaberus giganteus hemolymph hydrolyses JH methyl esters at a four-fold higher rate than JH ethyl esters, but does not hydrolyse JH n-propyl or n-butyl esters at measurable rates. (2Z,6E)-JH I ethyl ester, a significant by-product of the commonly utilized KCN-catalysed transesterification of (2E,6E)-JH I, is not hydrolysed by M. serta hemolymph or H. virescens recombinant JHE. (2Z,6E)-JH I ethyl ester and (2Z,6E)-JH I ethyl ester diol are metabolized at only slightly lower rates than the corresponding (2E,6E) isomers by M. sexta juvenile hormone epoxide hydrolase (JHEH) and JH diol phosphotransferase (JHDPT), respectively. (2E,6E)-JH I and (2E,6E)-JH I ethyl ester injected into M. serta larvae yield the same spectrum of metabolites, as do (2E,6E)-JH I diol and (2E,6E)-JH I ethyl ester diol. (2Z,6E)-JH I ethyl ester, however, is converted only to the diol and diol-phosphate metabolites by M. serta in vivo. (C) 1997 Elsevier Science Ltd.