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| {{STRUCTURE_2ggk| PDB=2ggk | SCENE= }} | | {{STRUCTURE_2ggk| PDB=2ggk | SCENE= }} |
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| '''The mutant A302C of Agrobacterium radiobacter N-carbamoyl-D-amino-acid amidohydrolase'''
| | ===The mutant A302C of Agrobacterium radiobacter N-carbamoyl-D-amino-acid amidohydrolase=== |
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| ==Overview==
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| N-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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_16650857}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 16650857 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_16650857}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: You, J Y.]] | | [[Category: You, J Y.]] |
| [[Category: N-carbamoyl-d-amino-acid amidohydrolase]] | | [[Category: N-carbamoyl-d-amino-acid amidohydrolase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 05:05:02 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 13:03:58 2008'' |
