The low reactivity of 5H-dibenzo[a, cflcycloheptene 10,ll-oxide in microsomal epoxide hydrolase catalysed hydration

Abstract

1. The rate of hydration of 5H-dibenzo[a, d]cycloheptene 10,11-oxide catalysed by rabbit liver microsomal epoxide hydrolase has been compared with that of the acyclic analogue cis-stilbene oxide. The latter was shown to be a much better substrate for the enzyme than the former epoxide.

2. The kinetic parameters for the hydration of 5H-dibenzo[a, d]cycloheptene 10,11-oxide and cis-stilbene oxide have been determined using a rabbit liver microsomal preparation at 37°C and pH 7·4. The much slower hydration of the former is due to a much lower Vs and not to a higher K_m relative to the latter epoxide.

3. 5H-Dibenzo[a, d]cycloheptene 10,11-oxide inhibited the hydration of cis-stilbene oxide by rabbit liver microsomal epoxide hydrolase.