<abstract xmlns="http://www.w3.org/1999/xhtml"><italic>Streptococcus iniae</italic> 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 <italic>S. iniae</italic> that was isolated from an infected Chinese sturgeon (<italic>Acipenser sinensis</italic>), as well as determined its biochemical characteristics and inhibitors. The <italic>alr</italic> 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. <italic>S. iniae</italic> Alr (SiAlr) could be inhibited by some metal ions, hydroxylamine and dithiothreitol (DTT). The kinetic parameters <italic>K</italic><italic>m</italic> and <italic>V</italic><italic>max</italic> 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.</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.

Purification, Characterization and Inhibition of Alanine Racemase from a Pathogenic Strain of <italic>Streptococcus iniae</italic>

Polish Journal of Microbiology

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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

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...

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

Article Category: original-paper

Published Online: Sep 03, 2019

Page range: 331 - 341

Received: Apr 21, 2019

Accepted: Jul 10, 2019

DOI: https://doi.org/10.33073/pjm-2019-036

Keywords
alanine racemase, inhibitors, homogentisic acid, hydroquinone and peptidoglycan

© 2019 Anton Pyskun et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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

Article Category: original-paper

Published Online: Sep 03, 2019

Page range: 331 - 341

Received: Apr 21, 2019

Accepted: Jul 10, 2019

DOI: https://doi.org/10.33073/pjm-2019-036

Keywordsalanine racemase, inhibitors, homogentisic acid, hydroquinone and peptidoglycan

© 2019 Anton Pyskun et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Keywords
alanine racemase, inhibitors, homogentisic acid, hydroquinone and peptidoglycan