MECHANISM OF ACTION AND CLONING OF EPOXIDE HYDROLASE FROM THE CABBAGE-LOOPER, TRICHOPLUSIA NI

The majority of the JH III epoxide hydrolase activity in last stadium day 3 (gate 1) wandering Trichoplusia ni was membrane bound with appro ximately 9% of the activity found in the cytosol. Both the microsomal and cytosolic JH epoxide hydrolases were stable, retaining 30% of thei r original activity after incubation at 4 degrees C for 15 days. O-18- labeled water underwent enzyme catalyzed regioselective addition to th e least substituted C10 position of JH III. In multiple turnover react ions with JH epoxide hydrolase in 97.9% O-18-labeled water, only 91.3% O-18 incorporation was observed. This is consistent with an S(N)2 rea ction likely involving a carboxylate in the active site of JH epoxide hydrolase. The DNA amplification cloning of a fragment of a putative T . ni epoxide hydrolase is reported. The deduced amino acid sequence sh ares 67% similarity to the rat microsomal epoxide hydrolase. (C) 1996 Wiley-Liss, Inc.