Nonpathogenic Mycobacterium species produce rare cyclic C(35) terpenes that are biosynthesized by cyclization of Z-type C(35) polyprenyl diphosphate. To provide deeper insight into the biosynthesis of C(35) terpenes, we carried out functional analyses of three Z-prenyltransferase homologues in M. vanbaalenii identified by genomic analysis. Mvan_3822, a novel bifunctional Z-prenyltransferase, biosynthesizes C(35)-heptaprenyl diphosphate as a main product from (E,E)-farnesyl diphosphate (E,E-FPP) and (E,E,E)-geranylgeranyl diphosphate (E,E,E-GGPP), but produces a C(50)-decaprenyl diphosphate from geranyl diphosphate. Mvan_1705 is a novel Z,E,E-GGPP synthase. In addition, novel cyclic C(35) terpenes, (14E)- and (14Z)-dehydroheptaprenylcycline, were identified as minor metabolites in nonpathogenic Mycobacterium cells. C(35) terpenes could be biosynthesized by two routes, in which E and Z geometric isomers of heptaprenyl diphosphate are produced from E,E-FPP and E,E,E-GGPP, and the prenylreductase responsible for the biosynthesis of C(35) terpenes could reduce both E and Z prenyl residues.
A search for C(35)-terpenes from non-saponified extracts of 12 non-pathogenic Mycobacterium species was carried out. Octahydroheptaprenyl mycolic acyl esters were isolated from M. chlorophenolicum cells which were also found from M. thermoresistibile, M. vanbaalenii, M. aichiense, M. smegmatis, and M. parafortuitum. This is the first report on a polyprenol esterified by a mycolate. A novel monocyclic C(35)-terpene possessing a ketone, named heptaprenylcycline B, was isolated, which was detected from M. chlorophenolicum and M. vanbaalenii. The biosynthetic pathway to heptaprenylcycline B was investigated with ancymidol which acts as an inhibitor of a P450 monooxygenase. This experiment suggested that the P450 monooxygenase may be responsible for the production of heptaprenylcycline B.
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