A Glutathione S -Transferase with Activity towards cis -1,2-Dichloroepoxyethane Is Involved in Isoprene Utilization by Rhodococcus sp. Strain AD45

Abstract

Rhodococcus sp. strain AD45 was isolated from an enrichment culture on isoprene (2-methyl-1,3-butadiene). Isoprene-grown cells of strain AD45 oxidized isoprene to 3,4-epoxy-3-methyl-1-butene,cis-1,2-dichloroethene tocis-1,2-dichloroepoxyethane, andtrans-1,2-dichloroethene totrans-1,2-dichloroepoxyethane. Isoprene-grown cells also degraded cis-1,2-dichloroepoxyethane andtrans-1,2-dichloroepoxyethane. All organic chlorine was liberated as chloride during degradation ofcis-1,2-dichloroepoxyethane. A glutathione (GSH)-dependent activity towards 3,4-epoxy-3-methyl-1-butene, epoxypropane,cis-1,2-dichloroepoxyethane, andtrans-1,2-dichloroepoxyethane was detected in cell extracts of cultures grown on isoprene and 3,4-epoxy-3-methyl-1-butene. The epoxide-degrading activity of strain AD45 was irreversibly lost upon incubation of cells with 1,2-epoxyhexane. A conjugate of GSH and 1,2-epoxyhexane was detected in cell extracts of cells exposed to 1,2-epoxyhexane, indicating that GSH is the physiological cofactor of the epoxide-transforming activity. The results indicate that a GSHS-transferase is involved in the metabolism of isoprene and that the enzyme can detoxify reactive epoxides produced by monooxygenation of chlorinated ethenes.

Bacterial sources and sinks of isoprene, a reactive atmospheric hydrocarbon

“…In recent work, the Janssen laboratory has unravelled many details of the biochemical pathway for isoprene degradation in Rhodococcus AD45, an isolate obtained from a freshwater sediment using isoprene as a sole carbon source (van Hylckama Vlieg et al, 1998;van Hylckama Vlieg, 1999). For this work, they used Rhodococcus AD45, an isolate obtained from a freshwater sediment enrichment with isoprene as sole carbon source.…”

“…Do these bacteria consume isoprene generated in soil, or do they take up atmospheric isoprene? In this regard, it will be interesting to determine the af®nity of the isoprene monooxygenase for isoprene; the K m for oxidation of isoprene by intact Rhodococcus cells is 0.8 mM (van Hylckama Vlieg et al, 1998). Levels of the hydrocarbon in forest canopies, even those dominated by isoprene-emitting species, rarely exceed 10 p.p.bv.…”

“…It will be of interest to see the completed enzymatic details of the catabolic pathway for isoprene in Rhodococcus and the relationship of this pathway to those for degradation of other natural and anthropogenic hydrodrocarbons. With work on recruiting catabolic genes for use in pollutant degradation by engineered microorganisms under way, it is likely that analysis of the gene products of the Rhodococcus isoprene pathway will be revealing; for example, several of the enzymes of the pathway have the potential to use chlorinated substrate analogues (van Hylckama Vlieg, 1999;van Hylckama Vlieg et al, 1998.…”

“…As reviewed by Conrad (1996), similar patterns of bacterial producers and consumers control emissions of other important atmospheric trace gases, such as CO,NO and N 2 O. From recently reported work, it appears that yet another bacterial source±sink phenomenon occurs with the volatile hydrocarbon, isoprene (2-methyl-1,3-butadiene). Isoprene emission has been detected from many different bacteria, especially bacilli Wagner et al, 1999a), soils have been shown to contain signi®cant levels of isoprene-consuming bacteria (Cleveland and Yavitt, 1997;1998), and progress has been made in unravelling the pathway for isoprene degradation in Rhodococcus (van Hylckama Vlieg et al, 1998;. This work may signal new interest in bacterial roles in bio-sphere±atmosphere exchange processes.…”

Identification and characterisation of isoprene‐degrading bacteria in an estuarine environment

“…The only isoprene sink studied in detail is photochemical degradation. However, microbes in soils readily degrade isoprene (Cleveland and Yavitt, 1998;Gray et al, 2015) and isoprene-degrading bacterial strains have been isolated, although most were not characterised in detail (van Ginkel et al, 1987a,b;Ewers et al, 1990;Cleveland and Yavitt, 1997;van Hylckama Vlieg et al, 1998). Recently, however, El Khawand et al (2016) showed that isoprenedegrading Rhodococcus spp.…”