Identification of a transglutaminase from Bacillus amyloliquefaciens: Gene mining, protein expression, mechanism analysis and enzymatic characterization

Transglutaminase (TGase) can catalyze the crosslinking within or between protein molecules, improving the structural and functional properties of proteins. It has been widely used in artificial meat, yogurt products, flour products and other foods. In this study, a high yield TGase strain was screened from fermented soybean, and it was identified as the Bacillus amyloliquefaciens XCT-09. Then, the transglutaminase (X9Tgl) from XCT-09 was expressed in Escherichia coli BL21(DE3), and the enzyme activity of purified X9Tgl reached 5.73 U/mg. Subsequently, the catalytic mechanism of X9Tgl was elucidated, and the X9Tgl contained the active center of E115, C116 and E187, as well as the substrate binding sites W149 and F69. Furthermore, this study characterized the enzymatic properties of X9Tgl, and the optimal catalytic temperature and pH were 60 °C and 6, respectively. Moreover, X9Tgl exhibited stronger thermal stability and pH tolerance than STG, and it was not inhibited by the majority of metal ions. This study successfully identified a X9Tgl with high thermal stability, and pH tolerance, which provided a potential TGase resource for application in the food and medicine fields.