Biosynthesis of Guatrypmethine C Implies Two Different Oxidases for <i>exo</i> Double Bond Installation at the Diketopiperazine Ring

Abstract

Heterologous expression of a silent gene cluster from Streptomyces cinnamoneus led to identification of guatrypmethine C, a guaninylated cyclo-l-Trp-l-Met derivative with two exo double bonds at the diketopiperazine ring. Structural elucidation was achieved using MS, 1H, 13C, and 15N NMR analyses including 1H–13C and 1H–15N HMBC. Gene combination and biochemical investigation proved that the formation of the two C═C bonds are catalyzed by two distinct enzyme families (i.e., cyclodipeptide oxidase and FeII/2OG-dependent oxygenase).

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