A Shinella β-N-acetylglucosaminidase of glycoside hydrolase family 20 displays novel biochemical and molecular characteristics.

Abstract

β-N-Acetylglucosaminidases (GlcNAcases) are important for many biological functions and industrial applications. In this study, a glycoside hydrolase family 20 GlcNAcase from Shinella sp. JB10 was expressed in Escherichia coli BL21 (DE3). Compared to many GlcNAcases, the purified recombinant enzyme (rJB10Nag) exhibited a higher specificity activity (538.8µmolmin-1mg-1) or V max (1030.0±82.1µmolmin-1mg-1) toward p-nitrophenyl β-N-acetylglucosaminide and N,N'-diacetylchitobiose (specificity activity of 35.4µmolmin-1mg-1) and a higher N-acetylglucosaminide tolerance (approximately 50% activity in 70.0mM N-acetylglucosaminide). The degree of synergy on enzymatic degradation of chitin by a commercial chitinase and rJB10Nag was as high as 2.35. The enzyme was tolerant to most salts, especially 3.0-15.0% (w/v) NaCl and KCl. These biochemical characteristics make the JB10 GlcNAcase a candidate for use in many potential applications, including processing marine materials and the bioconversion of chitin waste. Furthermore, the enzyme has the highest proportions of alanine (16.5%), glycine (10.5%), and random coils (48.8%) with the lowest proportion of α-helices (24.9%) among experimentally characterized GH 20 GlcNAcases from other organisms.