A GLUTATHIONE-S-TRANSFERASE WITH ACTIVITY TOWARDS CIS-1,2-DICHLOROEPOXYETHANE IS INVOLVED IN ISOPRENE UTILIZATION BY RHODOCOCCUS SP. STRAINAD45

Rhodococcus sp. strain AD45 was isolated from an enrichment culture on isoprene (2-methyl-1,3-butadiene). Isoprene-grown cells of strain AD4 5 oxidized isoprene to 3,4-epoxy-3-methyl-1-butene, cis-1,2 dichloroet hene to cis-1,2-dichloroepoxyethane, and trans-1,2-dichloroethene to t rans-1,2-dichloroepoxyethane. Isoprene-growth cells also degraded cis- 1,2-dichloroepoxyethane and trans-1,2-dichloroepoxyethane. All organic chlorine was liberated as chloride during degradation of cis-1,2-dich loroepoxyethane. A glutathione (GSH)-dependent activity towards 3,4-ep oxy-3-methyl-1-butene, epoxypropane, cis-1,2-dichloroepoxyethane, and trans-1,2-dichloroepoxyethane was detected in cell extracts of culture s grown on isoprene and 3,4-epoxy-3-methyl-1-butene. The epoxide-degra ding activity of strain AD45 was irreversibly lost upon incubation of cells with 1,2-epoxyhexane. A conjugate of GSN and 1,2-epoxyhexane was detected in cell extracts of cells exposed to 1,2-epoxyhexane, indica ting that GSH is the physiological cofactor of the epoxide-transformin g activity. The results indicate that a GSH S-transferase is involved in the metabolism of isoprene and that the enzyme can detoxify reactiv e epoxides produced by monooxygenation of chlorinated ethenes.