Biosynthesis of Several Oxyvinylglycine Nonproteinogenic Amino Acids Bearing Unusual Alkoxyamine Bonds

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Project Summary Natural products serve crucial roles in the pharmaceutical industry as drugs or leads for drug compounds. Generated through secondary metabolism, these molecules impact the virulence, symbiosis, and survival of microorganisms. The nonproteinogenic oxyvinylglycine amino acids are an interesting class of secondary metabolites characterized by the presence of a vinyl oxygen moiety. Members of this class, such as 4-(2’- aminoethoxy)vinylglycine (AVG), are known to arrest germination in plants by inhibiting the pyridoxal 5’- phosphate (PLP)-dependent enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase.2 While the biosynthesis of vinyl ether-bearing oxyvinylglycine nonproteinogenic amino acids including AVG has been explored, the formation of other members of the family with alternative functional groups remains undetermined. 4-Formylaminooxyvinylglycine (FVG), an oxyvinylglycine containing an N–O bond, was reported to have duel herbicidal and bactericidal activity.3,4 The gvg biosynthetic gene cluster in Pseudomonas fluorescens strain WH6 is responsible for the biosynthesis of FVG and the related compounds guanidinooxyvinylglycine (GOVG) and aminooxyvinylglycine (AOVG) though the exact biosynthetic mechanism remains unclear.5,6 In this proposal I will determine the biosynthetic pathways responsible for the formation of FVG, GOVG, and AOVG. I will use a combination of feeding experiments and in vitro biochemical assays to determine the substrate and product of each enzyme along the biosynthetic pathway of these three nonproteinogenic amino acids. The vinyl alkoxyamine is unusual in amino acids, therefore I will characterize the enzyme responsible for N–O bond construction and determine its chemical mechanism. These studies will facilitate the bioinformatic discovery of similar oxyvinylglycine nonproteinogenic amino acids. Moreover, characterization of the iron-dependent enzyme responsible for N–O bond formation will facilitate its use in a synthetic context to expand the repertoire of oxidative biocatalysts.