Biochemical Characterization and Phylogenetic Analysis of the Virulence Factor Lysine Decarboxylase From Vibrio vulnificus

• Published in: Frontiers in microbiology Vol. 9; p. 3082
• Main Authors: Han, Lifen, Yuan, Jinjin, Ao, Xiulan, Lin, Shujin, Han, Xiao, Ye, Hanhui
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 11.12.2018
• Subjects: biochemical characterization; lysine decarboxylase; Microbiology; phylogenetic analysis; Vibrio vulnificus; virulence factor; biochemical characterization; phylogenetic analysis; virulence factor; lysine decarboxylase; Vibrio vulnificus
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2018.03082

Cadaverine is produced in organisms from the amino acid lysine in a decarboxylation reaction catalyzed by lysine decarboxylase (EC 4.1.1.18). The inducible lysine decarboxylase CadA plays a vital role in acid stress response for enteric bacteria. is an extremely virulent human pathogen causing gastroenteritis when the acid conditions that prevent survival of in the stomach or small intestine are overcome. A gene encoding CadA was identified from . Subsequent analyses showed that CadA from (VvCadA) is a decamer with a 82-kDa subunit. Homogenous VvCadA was purified from and used for lysine decarboxylation with an optimal pH of 6.0 and optimal temperature of 37°C. The apparent and for lysine were 9.45 ± 0.24 μM/min and 0.45 ± 0.05 mM, respectively. Mutation analysis suggested that the amino-acid-binding pyridoxal phosphate, the cofactor of the enzyme, plays a vital role in the reaction. Mutation of the negatively charged residues interacting with lysine also affected the activity of the enzyme to some extent. Quantitative RT-PCR showed that expression of was up-regulated under low pH, low salinity, and oxidative stresses. Furthermore, the concentration of cadaverine released to the cell exterior also increased under these stresses. Protein sequence similarity network (SSN) analysis indicated that lysine decarboxylases with ornithine decarboxylases and arginine decarboxylases shared a common ancestor, and that lysine decarboxylases are more conserved during evolution. Our data provide evidence for the biochemical characteristics and important roles of VvCadA under stress conditions.