Expression and characterization of bile salt hydrolase from chicken and porcine Lactobacillus

Abstract:

[Objective] With the gradual prohibition of the use of antibiotic growth promoters (AGPs) in animal feed, studies on AGPs alternatives are becoming hot topics. As the bile salt hydrolase plays a key role in lipid metabolism, it has become an important direction in AGPs alternatives. This study is aimed to determine the difference in enzymatic properties of bile salt hydrolase from chicken and porcine Lactobacillus based on the prokaryotic expression and purification. [Methods] The encoding genes of chicken bile salt hydrolase (BSHc) and porcine bile salt hydrolase (BSHp) were expressed in E. coli and purified by His-tag affinity column chromatography. The purified products were used to identify the BSH kinetic properties by hydrolyzing the six glycoconjugated and tauroconjugated bile salts. Effects of temperature, pH and metal ion compounds on the BSH activity were also determined respectively. [Results] BSHc and BSHp displayed higher catalytic efficiencies on glycoconjugated bile salts than that of tauroconjugated bile salts, while BSHc had a slightly higher hydrolysis activity on glycoconjugated bile salts than BSHp. The higher enzymatic activity of BSHc and BSHp were observed at the temperature of 45 °C and 42 °C, respectively. The optimal pH for BSHc and BSHp were 6.0 and 5.4, respectively. The metal ion compounds containing Cu2+, Fe3+, Mn2+, and Zn2+ displayed different degrees of inhibition on BSHc and BSHp activity, especially higher inhibition observed in Cu2+ and Fe3+ compounds. The inhibition of the compounds containing Na+, K+, Mg2+, and Ca2+ on BSHc and BSHp activity was relatively weak or no inhibition, but KIO3 had a strong inhibitory effect on BSHc and BSHp activity, KI and CaCl2 also had strong inhibitory effects on BSHp activity. [Conclusion] Based on prokaryotic expression and protein purification, BSHc and BSHp displayed higher catalytic efficiencies on glycoconjugated bile salts than that of tauroconjugated bile salts. The optimal temperature and pH for BSHc was higher than that for BSHp. The metal ion compounds containing Cu2+, Fe3+, Mn2+, and Zn2+ displayed significant inhibition on BSHc and BSHp activity. The results will be helpful for identification of BSH inhibitors and development of AGPs alternatives.