1.13.11.50 evolution the enzyme belongs to the cupin superfamily of proteins 725553 1.13.11.50 additional information Dke1 also performs the atypical cleavage of the alpha-keto acid, 4-hydroxyphenylpyruvate, to form 4-hydroxybenzaldehyde as product instead of the homogentisate product found for 4-hydroxyphenylpyruvate with 4-hydroxyphenylpyruvate dioxygenase, EC 1.13.11.27, analysis of the bonding of the alpha-keto acid, 4-hydroxyphenylpyruvate, to ferrous Dke1 using anaerobic Dke1, added ferrous ammonium sulfate, and 4-hydroxyphenylpyruvate at pH 7.0, overview. active site was modeling, histidine residues are truncated to methyl imidazole for the model, and constraints imposed by the protein backbone are simulated by fixing the relative positions of the beta-carbons of the backbone. The coordination of the active site is completed with either alpha keto (monoanion) or enolate (dianion) bidentate coordinated 4-hydroxyphenylpyruvate ligand or a monoanionic acetylacetone ligand 725198 1.13.11.50 additional information Dke1 displays an atypical three-histidine metal binding site. Role of the protein structure in the catalysis of beta-diketone cleavage at the threehistidine metal center of diketone cleaving enzyme by computational methods in correlation with kinetic and mutational analyses. Molecular dynamics simulations, using quantum mechanically deduced parameters for the nonheme Fe(II) cofactor. Distinct organization of the hydrophilic triad in the free and substrate-ligated wild-type enzyme. In the free species, the Fe(II) center is coordinated to three histidines and one glutamate, whereas the substrate-ligated, catalytically competent enzyme-substrate complex has an Fe(II) center with three-histidine coordination, with a small fraction of three-histidine, one-glutamate coordination 725553