Characterization of Dextransucrase and Branching Sucrase of Apilactobacillus kunkeei DSM 12361

Abstract: Glycoside hydrolase family 70 (GH70) glucansucrases have various applications in both food and non-food industries. This study reports the characterization of two GH70 enzymes, dextransucrase and branching sucrase, of Apilactobacillus kunkeei DSM 12361 on a range of acceptor substrates. GtfZ of A. kunkeei DSM 12361 possesses two catalytic domains, CD1 and CD2, which are interconnected by a glucan binding domain (GBD). For this study, dextransucrase CD1-GBD is a combination of the first catalytic domain CD1 with GBD, while branching sucrase GBD-CD2 is composed of GBD combined with the second catalytic domain CD2. In addition to sucrose as the sole substrate, CD1-GBD was active when dextran was available as an acceptor substrate. It was also found that CD1-GBD was active on reuteran and modified potato amylose. GBD-CD2 was also active on various substrates such as dextran, reuteran, and modified amylose, which proves the ability of GBD-CD2 to introduce branches on polymer chains with different linkage types. The activity of CD1-GBD and GBD-CD2 showed a preference for α-(1→6) glycosidic linkage in the acceptor substrate. The ability of CD1-GBD and GBD-CD2 to act on starch-derived molecules, such as potato amylose, is crucial in synthesizing polymers at a low cost. The activity on a wide range of substrates increases the options for producing polymers with different properties.