1xpy
Structural Basis for Catalytic Racemization and Substrate Specificity of an N-Acylamino Acid Racemase Homologue from Deinococcus radiodurans
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OverviewOverview
N-acylamino acid racemase (NAAAR) catalyzes the racemization of, N-acylamino acids and can be used in concert with an aminoacylase to, produce enantiopure alpha-amino acids, a process that has potential, industrial applications. Here we have cloned and characterized an NAAAR, homologue from a radiation-resistant ancient bacterium, Deinococcus, radiodurans. The expressed NAAAR racemized various substrates at an, optimal temperature of 60 degrees C and had Km values of 24.8 mM and 12.3, mM for N-acetyl-D-methionine and N-acetyl-L-methionine, respectively. The, crystal structure of NAAAR was solved to 1.3 A resolution using, multiwavelength anomalous dispersion (MAD) methods. The structure consists, of a homooctamer in which each subunit has an architecture characteristic, of enolases with a capping domain and a (beta/alpha)7 beta barrel domain., The NAAAR.Mg2+ and NAAAR.N-acetyl-L-glutamine.Mg2+ structures were also, determined, allowing us to define the Lys170-Asp195-Glu220-Asp245-Lys269, framework for catalyzing 1,1-proton exchange of N-acylamino acids. Four, subsites enclosing the substrate are identified: catalytic site, metal-binding site, side-chain-binding region, and a flexible lid region., The high conservation of catalytic and metal-binding sites in different, enolases reflects the essentiality of a common catalytic platform, allowing these enzymes to robustly abstract alpha-protons of various, carboxylate substrates efficiently. The other subsites involved in, substrate recognition are less conserved, suggesting that divergent, evolution has led to functionally distinct enzymes.
About this StructureAbout this Structure
1XPY is a Single protein structure of sequence from Deinococcus radiodurans with MG and NLQ as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Structural basis for catalytic racemization and substrate specificity of an N-acylamino acid racemase homologue from Deinococcus radiodurans., Wang WC, Chiu WC, Hsu SK, Wu CL, Chen CY, Liu JS, Hsu WH, J Mol Biol. 2004 Sep 3;342(1):155-69. PMID:15313614
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