Requires non-heme-Fe(II). Isolated from some bacteria including Streptomyces hygroscopicus and Streptomyces viridochromogenes. The pro-R hydrogen at C-2 of the ethyl group is retained by the formate ion. Any stereochemistry at C-1 of the ethyl group is lost. One atom from dioxygen is present in each product. Involved in phosphinothricin biosynthesis.
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The enzyme appears in viruses and cellular organisms
the reaction proceeds via a transient iron(IV)-oxo (ferryl) complex, a mechanism that involves activation of an O-H bond by the ferryl complex is proposed. The isotope-sensitive C-H-cleavage step is not primarily rate-limiting for the overall catalytic cycle. The reaction does exhibit a significant 2H-kinetic isotope effect on kcat/Km for O2, which implies reversible formation of the C-H-cleaving intermediate
catalytic mechanism; initial substrate oxidation by a ferric-superoxo-intermediate and a second oxidation by a ferryl species, catalytic mechanism, detailed overview; the reaction proceeds via a transient iron(IV)-oxo (ferryl) complex, a mechanism that involves activation of an O-H bond by the ferryl complex is proposed. The isotope-sensitive C-H-cleavage step is not primarily rate-limiting for the overall catalytic cycle. The reaction does exhibit a significant 2H-kinetic isotope effect on kcat/Km for O2, which implies reversible formation of the C-H-cleaving intermediate
Requires non-heme-Fe(II). Isolated from some bacteria including Streptomyces hygroscopicus and Streptomyces viridochromogenes. The pro-R hydrogen at C-2 of the ethyl group is retained by the formate ion. Any stereochemistry at C-1 of the ethyl group is lost. One atom from dioxygen is present in each product. Involved in phosphinothricin biosynthesis.
all four electrons required for reduction of O2 are provided by the substrate. Occurence of an intermediate species in which oxygen derived from O2 exchanges with water
catalytic cycle is based on concatenated bifurcations. The first bifurcation is based on the abstraction of hydrogen atoms from the substrate, which leads to a distal or proximal hydroperoxo species Fe-OOH or Fe-(OH)O. The second and the third bifurcations refer to the carbon-carbon bond cleavage reaction achieved through a tridentate intermediate, or employing a proton-shuttle assisted mechanism, in which the residue Glu176 or the FeIV O group serves as a general base. The reaction directions seem to be tunable and show significant environment dependence
in the reaction mechanism water molecules serve as an oxygen source in the generation of mononuclear nonheme iron oxo complexes, taking part in the catalytic cycle before the carbon-carbon bond cleavage process. After the dioxygen is bound to the iron center, the dioxygen-bound species Fe-O2 is generated. The abstraction of hydrogen atom from the substrate leads to a distal or proximal hydroperoxo species Fe(III)-OOH. This is the rate-limiting step, which has an energy barrier of 21 and 18 kcal/mol for distal and proximal H-abstraction processes, respectively. The second step is the cleavage of the O-O bond, and the carbon-carbon bond is broken subsequently. In this step, a tridentate binding species and a Fe(IV) sigmaO species are important intermediates to break the carbon-carbon bond. In the third step, the formic acid and the intermediate CH2PO2(OH)- radical are generated. Finally, 2-hydroxyethylphosphonate is converted to hydroxymethylphosphonate, and the formate or formic acid is formed
mechanism involves removal of the pro-S hydrogen at C2 and the loss of stereochemical information at C1. Thus, the hydroperoxylation mechanism, previously proposed as the product of a Criegee rearrangement, cannot be operational for conversion of 2-hydroxyethylphosphonate
the reaction proceeds via a transient iron(IV)-oxo (ferryl) complex, the mechanism involves activation of an O-H bond by the ferryl complex. Maximal accumulation of the intermediate requires both the presence of deuterium in the substrate and, importantly, the use of 2H2O as solvent
the reaction proceeds via a transient iron(IV)-oxo (ferryl) complex, the mechanism involves activation of an O-H bond by the ferryl complex. Maximal accumulation of the intermediate requires both the presence of deuterium in the substrate and, importantly, the use of 2H2O as solvent
proper binding of 2-hydroxyethylphosphonate is important for O2 activation and the enzyme uses a compulsory binding order with 2-hydroxyethylphosphonate binding before O2. In the mechanism, a hydroperoxylation process is followed by a Criegee rearrangement and hydrolysis to form hydroxymethylphosphonate. Thereafter, the P-C bond in the product can be transiently broken, generating phosphite and formaldehyde in the active site of the enzyme. If the formaldehyde is able to rotate along the C=O bond, then phosphite can attack either face of the carbonyl group resulting in a loss of stereochemistry
reaction starts with H-abstraction from the C2 position of 2-hydroxyethylphosphonate by a ferric superoxide-type intermediate. The resultant Fe(II)-OOH intermediate may follow either a hydroperoxylation or hydroxylation pathway, the former process being energetically more favorable. In the hydroperoxylation pathway, a ferrous-alkylhydroperoxo intermediate is formed, and then its O-O bond is homolytically cleaved to yield a complex of ferric hydroxide with a gem-diol radical. Subsequent C-C bond cleavage within the gem-diol leads to formation of an R-CH2 radical species and one of the two products, i.e., formic acid. The R-CH2 radical then intramolecularly forms a C-O bond with the ferric hydroxide to provide the other product, hydroxymethylphosphonate. The overall reaction pathway requires ferric superoxide and ferric hydroxide intermediates
results provide strong support for a mechanism that proceeds by hydroperoxylation followed by a Criegee rearrangement with a phosphorus-based migrating group and requires that the O-O bond of molecular oxygen is not cleaved prior to substrate activation. No substrate: O-formyl-hydroxymethylphosphonate, (2S)-hydroxypropylphosphonate
HEPD oxidizes a relatively unactivated substrate that cannot easily facilitate O2 activation. 2-Hydroxyethylphosphonate does not contain a thiol group that upon binding to the iron can activate it for catalysis, nor does it contain an 2-oxo acid functionality
HEPD oxidizes a relatively unactivated substrate that cannot easily facilitate O2 activation. 2-Hydroxyethylphosphonate does not contain a thiol group that upon binding to the iron can activate it for catalysis, nor does it contain an 2-oxo acid functionality
2-hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS) are non-heme iron oxygenases that both catalyze the carbon-carbon bond cleavage of 2-hydroxyethylphosphonate but generate different products. Both HEPD and MPnS generate a methylphosphonate radical. Substrate labeling experiments lead to a mechanistic hypothesis in which the fate of a common intermediate determines product identity, overview. Primary sequences and homology modeling suggest that the architectures of the active sites of HEPD and MPnS are similar
one group of mononuclear non-heme iron-dependent enzymes includes 2-hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS, EC 1.13.11.73) that both carry out the oxidative cleavage of the carbon-carbon bond of 2-hydroxyethylphosphonate but generate different products. Common properties include the initial substrate oxidation by a ferric-superoxo-intermediate and a second oxidation by a ferryl species. Sequence homology between HEPD and MPnS combined with identical requirements for catalysis suggests a consensus mechanism in which product identity is determined by branching at an intermediate in the catalytic cycle
2-hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS) are non-heme iron oxygenases that both catalyze the carbon-carbon bond cleavage of 2-hydroxyethylphosphonate but generate different products. Both HEPD and MPnS generate a methylphosphonate radical. Substrate labeling experiments lead to a mechanistic hypothesis in which the fate of a common intermediate determines product identity, overview. Primary sequences and homology modeling suggest that the architectures of the active sites of HEPD and MPnS are similar; one group of mononuclear non-heme iron-dependent enzymes includes 2-hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS, EC 1.13.11.73) that both carry out the oxidative cleavage of the carbon-carbon bond of 2-hydroxyethylphosphonate but generate different products. Common properties include the initial substrate oxidation by a ferric-superoxo-intermediate and a second oxidation by a ferryl species. Sequence homology between HEPD and MPnS combined with identical requirements for catalysis suggests a consensus mechanism in which product identity is determined by branching at an intermediate in the catalytic cycle
2-hydroxyethylphosphonate dioxygenase (HEPD) cleaves the C1-C2 bond of its substrate to afford hydroxymethylphosphonate on the biosynthetic pathway to the commercial herbicide phosphinothricin
2-hydroxyethylphosphonate dioxygenase (HEPD) cleaves the C1-C2 bond of its substrate to afford hydroxymethylphosphonate on the biosynthetic pathway to the commercial herbicide phosphinothricin
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
in vitro reconstitution of activity and determination of the crystal structure of Cd2+-substituted PhpD in complex with the 2-hydroxyethylphosphonate substrate
to 1.8 A resolution. The overall structure consists of imperfect tandem repeats of a bi-domain architecture. Each of the repeats is composed of an all-alpha-helical domain linked to a beta-barrel fold characteristic of the cupin superfamily. A Cd(II) ion is situated at the base of the active site and is coordinated by residues His 129, Glu 176 and His 182
site-directed mutagenesis, the mutant enzyme shows similar activity as the wild-type enzyme. Like the wild-type enzyme, the mutant HEPD-E176A produces hydroxymethylphosphonate and formate as its only detectable products upon incubation with Fe(II), hydroxyethylphosphonate, and O2
site-directed mutagenesis, the mutant is bifunctional exhibiting the activity of both 2-hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS, EC 1.13.11.73). The product distribution of the mutant is sensitive to a substrate isotope effect, consistent with an isotope-sensitive branching mechanism involving a common intermediate. The introduced histidine does not coordinate the active site metal, unlike the iron-binding glutamate it replaces. More HEPD activity is observed when the reaction is carried out with (R)-2-[2-2H1]-hydroxyethylphosphonate
site-directed mutagenesis, the mutant enzyme shows similar activity as the wild-type enzyme. Like the wild-type enzyme, the mutant HEPD-E176A produces hydroxymethylphosphonate and formate as its only detectable products upon incubation with Fe(II), hydroxyethylphosphonate, and O2
site-directed mutagenesis, the mutant is bifunctional exhibiting the activity of both 2-hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS, EC 1.13.11.73). The product distribution of the mutant is sensitive to a substrate isotope effect, consistent with an isotope-sensitive branching mechanism involving a common intermediate. The introduced histidine does not coordinate the active site metal, unlike the iron-binding glutamate it replaces. More HEPD activity is observed when the reaction is carried out with (R)-2-[2-2H1]-hydroxyethylphosphonate
Ferric superoxide and ferric hydroxide are used in the catalytic mechanism of hydroxyethylphosphonate dioxygenase: a density functional theory investigation
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Enzyme Nomenclature
1.13.11.72 2-hydroxyethylphosphonate dioxygenase
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