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Title: In vitro Characterization of Enzymes Involved in the Synthesis of Nonproteinogenic Residue (2S, 3S)-beta-Methylphenylalanine in Glycopeptide Antibiotic Mannopeptimycin
Authors: Tsung-Lin Li
Yu-Ting Huang
Syue-Yi Lyu
Pei-Hsuan Chuang
Ning-Shian Hsu
Yi-Shan Li
Hsiu-Chien Chan
Chuen-Jiuan Huang
Yu-Chen Liu
Chang-Jer Wu
Wen-Bin Yang
Contributors: 國立臺灣海洋大學:食品科學系
Date: 2009-10
Issue Date: 2016-12-12T08:42:55Z
Publisher: Chembiochem
Abstract: Abstract: Mannopeptimycin, a potent drug lead, has superior activity against difficult-to-treat multidrug-resistant Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). (2S,3S)-beta-Methylphenylalanine is a residue in the cyclic hexapeptide core of mannopeptimycin, but the synthesis of this residue is far from clear. We report here on the reaction order and the stereochemical course of reaction in the formation of (2S,3S)-beta-methylphenylalanine. The reaction is executed by the enzymes MppJ and TyrB, an S-adenosyl methionine (SAM)-dependent methyltransferase and an (S)-aromatic-amino-acid aminotransferase, respectively. Phenylpyruvic acid is methylated by MppJ at its benzylic position at the expense of one equivalent of SAM. The resulting beta-methyl phenylpyruvic acid is then converted to (2S,3S)-beta-methylphenylalanine by TyrB. MppJ was further determined to be regioselective and stereoselective in its catalysis of the formation of (3S)-beta-methylphenylpyruvic acid. The binding constant (K(D)) of MppJ versus SAM is 26 microM. The kinetic constants with respect to k(cat Ppy) and K(M Ppy), and k(cat SAM) and K(M SAM) are 0.8 s(-1) and 2.5 mM, and 8.15 s(-1) and 0.014 mM, respectively. These results suggest SAM has higher binding affinity for MppJ than Ppy, and the C--C bond formation in betamPpy might be the rate-limiting step, as opposed to the C--S bond breakage in SAM.
Relation: 10(15)
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/39447
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