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Background   N -Acetyl glucosamine (GlcNAc) and  N -Acetyl chitooligosaccharides ( N -Acetyl COSs) exhibit many biological activities, and have been widely used in the pharmaceutical, agriculture, food, and chemical industries. Particularly, higher  N -Acetyl COSs with degree of polymerization from 4 to 7 ((GlcNAc) 4 –(GlcNAc) 7 ) show good antitumor and antimicrobial activity, as well as possessing strong stimulating activity toward natural killer cells. Thus, it is of great significance to discover a β- N -acetyl glucosaminidase (NAGase) that can not only produce GlcNAc, but also synthesize  N -Acetyl COSs.    Results  The gene encoding the novel β- N -acetyl glucosaminidase, designated  Cm NAGase, was cloned from  Chitinolyticbacter meiyuanensis  SYBC-H1. The deduced amino acid sequence of  Cm NAGase contains a glycoside hydrolase family 20 catalytic module that shows low identity (12–35%) with the corresponding domain of most well-characterized NAGases. The  Cm NAGase gene was highly expressed with an active form in  Escherichia coli  BL21 (DE3) cells. The specific activity of purified  Cm NAGase toward  p -nitrophenyl- N -acetyl glucosaminide ( p NP-GlcNAc) was 4878.6 U/mg of protein.  Cm NAGase had a molecular mass of 92 kDa, and its optimum activity was at pH 5.4 and 40 °C. The  V  max ,  K  m ,  K  cat , and  K  cat / K  m  of  Cm NAGase for  p NP-GlcNAc were 16,666.67 μmol min −1  mg −1 , 0.50 μmol mL −1 , 25,555.56 s −1 , and 51,111.12 mL μmol −1  s −1 , respectively. Analysis of the hydrolysis products of  N -Acetyl COSs and colloidal chitin revealed that  Cm NAGase is a typical exo-acting NAGase. Particularly,  Cm NAGase can synthesize higher  N -Acetyl COSs ((GlcNAc) 3 –(GlcNAc) 7 ) from (GlcNAc) 2 –(GlcNAc) 6 , respectively, showed that it possesses transglycosylation activity. In addition,  Cm NAGase also has reverse hydrolysis activity toward GlcNAc, synthesizing various linked GlcNAc dimers.    Conclusions  The observations recorded in this study that  Cm NAGase is a novel NAGase with exo-acting, transglycosylation, and reverse hydrolysis activities, suggest a possible application in the production of GlcNAc or higher  N -Acetyl COSs.

A novel bacterial β-N-acetyl glucosaminidase from Chitinolyticbacter meiyuanensis possessing transglycosylation and reverse hydrolysis activities