Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/60304
標題: Biochemical characterization of a novel lysine racemase from Proteus mirabilis BCRC10725
作者: Kuan, Yi-Chia
Kao, Chao-Hung
Chen, Chao-Hsien
Chen, Chang-Chih
Hu, Hui-Yu
Hsu, Wen-Hwei
關鍵字: Proteus mirabilis
Lysine racemase
Lysine racemization
Arginine
racemization
PLP-dependent enzyme
Substrate specificity
amino-acid racemases
bacterial-cell wall
alanine racemase
crystal-structure
bacillus-stearothermophilus
glutamate racemase
pseudomonas-p
摘要: A lysine racemase gene (lyr) that consisted of an open reading frame of 1224-bp and encoded a protein with a calculated molecular mass of 45 kDa was cloned from the Proteus mirabilis BCRC10725 and expressed in Escherichia coli BL21(DE3). The purified Hiss-tagged Lyr was most active towards lysine, exhibiting a specific activity of 2828 +/- 97 U/mg. This enzyme also racemized arginine with a specific activity of 568 +/- 28 U/mg but not other amino acids. The optimal conditions for Lyr activity to L-lysine were pH 8.0-9.0 and 50 degrees C. The racemization activity of Lyr was completely inhibited by 5 mM hydroxy-lamine and was partially restored by the addition of pyridoxal 5'-phosphate. The S394 residue of Lyr was subjected to site-directed mutagenesis. The arginine racemization activities of the S394Y, S394N, S394C and S394T variant proteins were increased by 1.5-1.8 fold compared to the wild-type Lyr, indicating that the S394 residue played a crucial role in determining the preference of Lyr to lysine and arginine. (C) 2011 Elsevier Ltd. All rights reserved.
URI: http://hdl.handle.net/11455/60304
ISSN: 1359-5113
Appears in Collections:分子生物學研究所

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