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Purification, Characterization and Inhibition of Alanine Racemase from a Pathogenic Strain of Streptococcus iniae Cover

Purification, Characterization and Inhibition of Alanine Racemase from a Pathogenic Strain of Streptococcus iniae

Open Access
|Sep 2019

Abstract

Streptococcus iniae is a pathogenic and zoonotic bacteria that impacted high mortality to many fish species as well as capable of causing serious disease to humans. Alanine racemase (Alr, EC 5.1.1.1) is a pyridoxal-5’-phosphate (PLP)-containing homodimeric enzyme that catalyzes the racemization of L-alanine and D-alanine. In this study, we purified alanine racemase from S. iniae that was isolated from an infected Chinese sturgeon (Acipenser sinensis), as well as determined its biochemical characteristics and inhibitors. The alr gene has an open reading frame (ORF) of 1107 bp, encoding a protein of 369 amino acids, which has a molecular mass of 40 kDa. The enzyme has optimal activity at a temperature of 35°C and a pH of 9.5. It belongs to the PLP-dependent enzymes family and is highly specific to L-alanine. S. iniae Alr (SiAlr) could be inhibited by some metal ions, hydroxylamine and dithiothreitol (DTT). The kinetic parameters Km and Vmax of the enzyme were 33.11 mM, 2426 units/mg for L-alanine, and 14.36 mM, 963.6 units/mg for D-alanine. Finally, the 50% inhibitory concentrations (IC50) values and antibiotic activity of two alanine racemase inhibitors (homogentisic acid and hydroquinone), were determined and found to be effective against both Gram-positive and Gram-negative bacteria employed in this study.

DOI: https://doi.org/10.33073/pjm-2019-036 | Journal eISSN: 2544-4646 | Journal ISSN: 1733-1331
Language: English
Page range: 331 - 341
Submitted on: Apr 21, 2019
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Accepted on: Jul 10, 2019
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Published on: Sep 3, 2019
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year

© 2019 MURTALA MUHAMMAD, YANGYANG LI, SIYU GONG, YANMIN SHI, JIANSONG JU, BAOHUA ZHAO, DONG LIU, published by Polish Society of Microbiologists
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.