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From Proteopedia
The mutant A68C-D72C of Deinococcus Radiodurans N-acylamino acid racemase
Structural highlights
FunctionNSAR_DEIRA Acts as a N-succinylamino acid racemase (NSAR) that catalyzes the racemization of N-succinyl-L-phenylglycine and N-succinyl-D/L-phenylalanine (PubMed:24872444, PubMed:25875730). Can catalyze the racemization of a broad range of N-acylamino acids, including N-acetyl-D/L-methionine, N-acetyl-D/L-phenylalanine, N-acetyl-L-glutamine, N-acetyl-L-tryptophan, N-acetyl-L-leucine, N-formyl-D-methionine, N-formyl-D-norleucine, N-carbamoyl-D-methionine and N-carbamoyl-D-norleucine (PubMed:15313614, PubMed:16650857, PubMed:25875730). Also converts 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) to 2-succinylbenzoate (OSB) (PubMed:24872444). Catalyzes both N-succinylamino acid racemization and OSB synthesis at equivalent rates (PubMed:24872444). However, NSAR activity is probably the protein's biological function, because menaquinone biosynthesis genes are missing in this species (Probable).[1] [2] [3] [4] [5] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedN-Acylamino acid racemase (NAAAR) and N-carbamoyl-D-amino-acid amidohydrolase (D-NCAase) are important biocatalysts for producing enantiopure alpha-amino acids. NAAAR forms an octameric assembly and displays induced fit movements upon substrate binding, while D-NCAase is a tetramer that does not change conformation in the presence of a ligand. To investigate the effects of introducing potentially stabilizing S-S bridges in these different multimeric enzymes, cysteine residues predicted to form inter or intra-subunit disulfide bonds were introduced by site-directed mutagenesis. Inter-subunit S-S bonds were formed in two NAAAR variants (A68C-D72C and P60C-Y100C) and two d-NCAase variants (A302C and P295C-F304C). Intra-subunit S-S bonds were formed in two additional NAAAR variants (E149C-A182C and V265C). Crystal structures of NAAARs variants show limited deviations from the wild-type overall tertiary structure. An apo A68C-D72C subunit differs from the wild-type enzyme, in which it has an ordered lid loop, resembling ligand-bound NAAAR. The structures of A222C and A302C D-NCAases are nearly identical to the wild-type enzyme. All mutants with inter-subunit bridges had increases in thermostability. Compared with the wild-type enzyme, A68C-D72C NAAAR showed similar kcat/Km ratios, whereas mutant D-NCAases demonstrated increased kcat/Km ratios at high temperatures (A302C: 4.2-fold at 65 degrees C). Furthermore, molecular dynamic simulations reveal that A302C substantially sustains the fine-tuned catalytic site as temperature increases, achieving enhanced activity. Structure-stability-activity relationship in covalently cross-linked N-carbamoyl D-amino acid amidohydrolase and N-acylamino acid racemase.,Chiu WC, You JY, Liu JS, Hsu SK, Hsu WH, Shih CH, Hwang JK, Wang WC J Mol Biol. 2006 Jun 9;359(3):741-53. Epub 2006 Apr 18. PMID:16650857[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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