Property and Function of a Novel Chitinase Containing Dual Catalytic Domains Capable of Converting Chitin Into N-Acetyl-D-Glucosamine

A novel multifunctional chitinase ( Cm Chi3)-encoding gene was cloned from Chitinolyticbacter meiyuanensis and actively expressed in Escherichia coli . Sequence analysis showed that Cm Chi3 contains two glycoside hydrolase family 18 (GH18) catalytic domains and exhibited low identity with well-characterized chitinases. The optimum pH and temperature of purified recombinant Cm Chi3 were 6.0 and 50°C, respectively. Cm Chi3 exhibited strict substrate specificity of 4.1 U/mg toward colloidal chitin (CC) and hydrolyzed it to yield N -acetyl-D-glucosamine (GlcNAc) as the sole end product. An analysis of the hydrolysis products toward N -acetyl chitooligosaccharides ( N -acetyl COSs) and CC substrates revealed that Cm Chi3 exhibits endochitinase, N -acetyl-β-d-glucosaminidase (NAGase), and transglycosylase (TGase) activities. Further studies revealed that the N-terminal catalytic domain of Cm Chi3 exhibited endo-acting and NAGase activities, while the C-terminal catalytic domain showed exo-acting and TGase activities. The hydrolytic properties and favorable environmental adaptations indicate that Cm Chi3 holds potential for commercial GlcNAc production from chitin.