Biosynthetic Origin of Formylaminooxyvinylglycine and Characterization of the Formyltransferase GvgI

Abstract

4-Formylaminooxyvinylglycine (FVG) is an herbicidal and antibacterial nonproteinogenic amino acid produced by several strains of the Pseudomonas fluorescens species complex. It contains a unique vinyl alkoxyamine moiety with an O–N bond, and its biosynthetic origin remains unknown. Here, we show that the gvg cluster from P. fluorescens WH6 is responsible for the biosynthesis of FVG and two additional O–N bond-containing oxyvinylglycines, guanidinooxyvinylglycine and aminooxyvinylglycine. Feeding studies in the producing bacteria indicate that these compounds originate from homoserine. We identify a formyltransferase gvgI that is required for the production of FVG and characterize the activity of this enzyme in vitro toward amino acids with a side chain amine. Sequence similarity network analysis reveals that GvgI and homologues make up a distinct group from the main classes of formyltransferases.

In vitro characterization of nonribosomal peptide synthetase-dependent O-(2-hydrazineylideneacetyl)serine synthesis indicates a stepwise oxidation strategy to generate the α-diazo ester moiety of azaserine

“…[47][48][49] AzsE also shows a weak similarity (27% identity) to GvgC, which was shown to be involved in the biosynthesis of 4-formylaminooxyvinylglycine in Pseudomonas uorescens WH6 by gene inactivation experiments. 50,51 AzsG is a cytochrome P450 with a weak similarity (24.7% identity) to SAMR0479 in stambomycin A biosynthesis in Streptomyces ambofaciens ATCC23877. 52 SAMR0479 was shown to catalyze C-H oxidation to produce a hydroxy group.…”

Characterization of GvgD and GvgH encoded in the biosynthetic gene cluster of 4-formylaminooxyvinylglycine

“…Just like rhizobitoxine, l -homoserine has been proved to be the precursor of FVG very recently. 13 We hypothesize that the aminooxy group in FVG is installed via an elimination–addition process akin to the biosynthesis of rhizobitoxine and d -cycloserine, another aminooxy containing natural product (Fig. S2†).…”

“…1B). 13 In this work, we characterize the activity of GvgD in vitro for the reversible amidinylation between l -canaline ( 2 ) and l -ornithine. Moreover, further studies also unveil that GvgH catalyzes the γ-elimination of O -succinylhomoserine (OSHS, 4 ) and O -acetylhomoserine (OAHS, 5 ), and that this enzyme may well take part in the formation of the oxyvinylglycine core in FVG.…”

“…1A). 13 Despite the structural similarities of the oxyvinylglycines above, distinct biosynthetic logics are employed to constitute the oxyvinyl moieties (Fig. S2 †).…”