Enzymatic Conversion of Cyclohexane to Cyclohexanol by Isolated Rat Liver Microsomes (MS)

Abstract

Normal rat liver MS possess little if any ability to convert medium chain length hydrocarbons (HC) to the corresponding primary alcohols in vitro. Pretreatment of MS donor animals with phenobarbital (75 mg/kg body wt., IP injection, daily for 5 days) resulted in MS with a slight but detectable ability to convert these HC to their primary alcohols in vitro (Table I). MS isolated from phenobarbital-treated rats converted cyclohexane to cycohexanol at rates 11–128 times those of the n-HC. Maximum cyclohexanol production was observed in the presence of pyrophosphate, nicotinamide, and an NADPH regenerating system. This presumably was due to the inhibition of various NADP (H) degrading enzymes such as NADP ase, NADP (H) pyrophosphatase, and NADPH oxidase present in the MS. NADH could not substitute for NADPH. Cyclohexanol production was maximal at pH 7.4 (0.1 M phosphate buffer) and at a temperature of 37°C. Yields of cyclohexanol increased with increasing MS protein up to a maximum of about 13 mg/ml of reaction mixture. The time course of cyclohexanol production was biphasic, being rapid for the first 30 min followed by a much slower but linear rate of production for as long as 3 hr. A variety of compounds were found to inhibit the production of cyclohexanol, in particular sodium dodecyl sulfate and the medium chain n-alcohols.