Tissue distribution and substrate specificity of an epoxide hydrase in the gypsy moth,Lymantria dispar

Abstract

Abstract. The stereoselectivity of the enzymatic hydration of disparlure, the pheromon e for the gypsy moth Lymantria dispar, and for two meso analogues was determined. A single epoxide hydrase (EH), present in various male and female moth tissues, converted disparlure and the analogues to their respective threo-(R,R)-diols with high stereoselectivity as determined by analysis of the diols by chiral phase capillary gas chromatography. This EH recognizes the cis-nature of the dialkyl oxirane, but shows poor discrimination of the two alkyl chains. Key words. Pheromone analogue; substrate analogue; disparlure; Lymantria dispar; gypsy moth; epoxide hydrase; pheromone metabolism; lipophilic site; epoxide; oxirane; stereoselective hydration. threo-(7R,8R)-diol enantiomer stereoselectively; that is ( +)-(7R,8S)-, (-)-(7S,8R)-, and racemic disparlure were all converted to the (7R,8R)-diol with enantiomeric excesses of > 92 % as determined by analysis of the derivatized diols by chiral phase capillary gas chromatography (CP-CGC) 11. In this study, we determined the stereoselectivity of the hydration of racemic disparlure by the EH derived from male antennae (MA), male legs (ML), female antennae (FA), and female legs (FL). The stereoselectivity of the male antennal EH-mediated reaction on two meso-analogues of disparlure (2 and 3, fig. 1) was also examined.In all cases, the threo-(R,R)-diol was the major product.These results suggested that same EH was present in the four L. dispar tissues studied. Furthermore, it appears that the orientation of the oxirane ring in the active site of the EH, rather than a particular arrangement of alkyl side-chains, is what determines the stereochemical outcome of the hydration. The synthesis of disparlure stereoisomers (+)-1, (-)-1, (_+)-1, and the meso-straight-chain oxirane 2 was described previously 1~ The synthesis of meso-branchedchain oxirane 3 is shown in scheme 1. The meso-oxirane 3 was obtained after eleven steps in 15 % overall yield 12.All intermediates and meso-oxirane 3 were characterized by 300 MHz 1H and 75 MHz 13C NMR spectroscopy, low-resolution gas chromatography/mass spectrometry, and were either homogeneous by thin-layer chromatography or were >95% pure by CGC. In addition, meso-oxirane 3 also gave a satisfactory high-resolution

Role of epoxide hydrolases in lipid metabolism

“…Rapid degradation of a pheromone following its initial detection is critical for the insect to orient itself in a dynamic way. For compounds like disparlure, some EHs can play this role in the insect antenna [33]. Recently, an EH that hydrolyzes the epoxide of vernolic acid was shown to be involved in the biosynthesis of a pheromone in the jewel wasp Nasonia vitripennis [34].…”