An unusual carbon–carbon bond cleavage reaction during phosphinothricin biosynthesis

Abstract

Natural products containing phosphorus-carbon bonds have found widespread use in medicine and agriculture1. One such compound, phosphinothricin tripeptide (PTT), contains the unusual amino acid phosphinothricin (PT) attached to two alanine residues (Fig. 1). Synthetic PT (glufosinate) is a component of two top-selling herbicides (Basta® and Liberty®), and is widely used with resistant transgenic crops including corn, cotton and canola. Recent genetic and biochemical studies showed that during PTT biosynthesis 2-hydroxyethylphosphonate (HEP) is converted to hydroxymethylphosphonate (HMP) (Fig. 1)2. Reported here are the in vitro reconstitution of this unprecedented C(sp3)-C(sp3) bond cleavage reaction and X-ray crystal structures of the enzyme. The protein is a mononuclear non-heme iron(II)-dependent dioxygenase that converts HEP to HMP and formate. In contrast to most other members of this family, the oxidative consumption of HEP does not require additional cofactors or the input of exogenous electrons. The current study expands the scope of reactions catalyzed by the 2-His-1-carboxylate mononuclear non-heme iron family of enzymes.

Characterization and structure of DhpI, a phosphonate O -methyltransferase involved in dehydrophos biosynthesis

“…Discussion PEP mutase (PEPM) installs the P-C bond in all phosphonates for which the biosynthetic gene clusters are currently known. As part of a multidisciplinary program focused on naturally occurring phosphonates we have recently demonstrated that the gene clusters of these compounds can be readily identified using the pepM gene as a marker (3)(4)(5)(6)(7)(8)(9)(10). In addition, these studies have shown that phosphonate biosynthesis is widespread and that new clusters that encode for as yet structurally unidentified phosphonates are readily found (1).…”

“…Other members mimic carboxyl groups or the tetrahedral intermediates formed during enzymatic metabolism of these moieties. Recent studies have started to reveal nature's biosynthetic strategies toward several of these compounds, including the clinically used antibiotic fosfomycin (2)(3)(4), the antimalaria clinical candidate FR900098 (5,6), the antifungal tripeptide rhizocticin (7), and the widely used herbicide phosphinothricin (8)(9)(10)(11)(12) (Fig. 1A).…”

Oxidative Decarboxylation of Benzilic Acid by a Biomimetic Iron(II) Complex: Evidence for an Iron(IV)–Oxo–Hydroxo Oxidant from O2

“…As we have previously shown that iron(III)-superoxide species derived from related biomimetic nonheme iron complexes are capable of hydrogen-atom abstraction from CÀH or OÀH groups, [8,12] we propose that the bound superoxide radical of the 1·O 2 adduct abstracts the hydrogen atom from the OH group of benzilate to form an iron(III)-hydroperoxide species and a bound benzilate oxyl radical. The latter spontaneously decomposes, resulting in C À C bond cleavage to form benzophenone and CO 2 …”

Structural basis for methylphosphonate biosynthesis

“…1). MPnS is similar in sequence to hydroxyethylphosphonate dioxygenase (HEPD) (11) and hydroxypropylphosphonate epoxidase (HppE) (10, 12), which catalyze the formation of hydroxymethylphosphonate (HMP) from 2-HEP (Fig. 1) (11) and the formation of the antibiotic fosfomycin from 2- S -hydroxypropylphosphonate (13), respectively.…”

“…2A and S3A). The position of Gln152 in MPnS is distinct from that of the iron coordinating Glu (E176) in Sv HEPD (11), originating from an adjacent β-strand at the analogous position of the iron-coordinating Glu in HppE (12) (Fig. S2B).…”