stereospecific hydrogen transfer of the pro-R hydrogen at C2 of the substrate to the methyl group of methylphosphonate. Neither hydrogen transfer is rate limiting under saturating substrate conditions
the pro-(R) hydrogen at C2 of 2-hydroxyethylphosphonate is quantitatively incorporated by enzyme MPnS into methylphosphonate. AN irreversible step involving O2
a mononuclear non-heme iron-dependent enzyme. MPnS contains iron-binding residues at only the two histidines, raising the specter that either MPnS is a 2-His only enzyme or that the third ligand is not well conserved in the alignment
apo MPnS homology modeling using the crystal structure of Cd2+-substituted HEPD, EC 1.13.11.72, in complex with substrate 2-hydroxyethylphosphonate, PDB ID 3GBF
2-hydroxyethylphosphonate dioxygenase (HEPD, EC 1.13.11.72) 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, EC 1.13.11.72) and methylphosphonate synthase (MPnS) 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
site-directed mutagenesis, the HEPD, EC 1.13.11.72, mutant is bifunctional exhibiting the activity of both 2-hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS). 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
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Enzyme Nomenclature
1.13.11.73 methylphosphonate synthase
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