Biochemical characterization of a β-N-acetylhexosaminidase from Catenibacterium mitsuokai suitable for the synthesis of lacto-N-triose II

Abstract

β-N-acetylhexosaminidases have gained much attention for synthesis of functional oligosaccharides, but the relatively low conversion ratio limited their industrial applications. A β-N-acetylhexosaminidase gene (CmHex187) from Catenibacterium mitsuokai was successfully expressed in Escherichia coli. The recombinant enzyme (CmHex187) was purified, biochemically characterized and subjected to the synthesis of human milk oligosaccharides (HMOs). CmHex187 displayed optimal pH and temperature of 5.5 and 45 °C, respectively. The enzyme showed strong transglycosylation activity, as it efficiently catalyzed the synthesis of an important component of HMO lacto-N-triose II (LNT2) using 0.015 M p-nitrophenyl N-acetyl-β-d-glucosaminide and 1.2 M lactose at pH 7.0 and 60 °C for 1.5 h, with a high conversion ratio of 44.3 %. The formed LNT2 promoted the growth of tested Lactobacillus and Bifidobacteria strains. The excellent enzymatic properties and high LNT2 synthesis ability of CmHex187 may make it a good candidate in LNT2 production.