AUTHOR=Zhang Alei , Mo Xiaofang , Zhou Ning , Wang Yingying , Wei Guoguang , Hao Zhikui , Chen Kequan 

TITLE=Identification of Chitinolytic Enzymes in Chitinolyticbacter meiyuanensis and Mechanism of Efficiently Hydrolyzing Chitin to N-Acetyl Glucosamine

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.572053

DOI=10.3389/fmicb.2020.572053

ISSN=1664-302X

ABSTRACT=<p><italic>Chitinolyticbacter meiyuanensis</italic> SYBC-H1, a bacterium capable of hydrolyzing chitin and shrimp shell to <italic>N</italic>-acetyl glucosamine (GlcNAc) as the only product, was isolated previously. Here, the hydrolysis mechanism of this novel strain toward chitin was investigated. Sequencing and analysis of the complete genome of SYBC-H1 showed that it encodes 32 putatively chitinolytic enzymes including 30 chitinases affiliated with the glycoside hydrolase (GH) families 18 (26) and 19 (4), one GH family 20 β-<italic>N</italic>-acetylglucosaminidase (NAGase), and one Auxiliary Activities (AA) family 10 lytic polysaccharide monooxygenase (LPMO). However, only eight GH18 chitinases, one AA10 LPMO, and one GH20 NAGase were detected in the culture broth of the strain, according to peptide mass fingerprinting (PMF). Of these, genes encoding chitinolytic enzymes including five GH18 chitinases (<italic>Cm</italic>711, <italic>Cm</italic>3636, <italic>Cm</italic>3638, <italic>Cm</italic>3639, and <italic>Cm</italic>3769) and one GH20 NAGase (<italic>Cm</italic>3245) were successfully expressed in active form in <italic>Escherichia coli</italic>. The hydrolysis of chitinous substrates showed that <italic>Cm</italic>711, <italic>Cm</italic>3636, <italic>Cm</italic>3638, and <italic>Cm</italic>3769 were endo-chitinases and <italic>Cm</italic>3639 was exo-chitinase. Moreover, <italic>Cm</italic>3639 and <italic>Cm</italic>3769 can convert the GlcNAc dimer and colloidal chitin (CC) into GlcNAc, which showed that they also possess NAGase activity. In addition, NAGase <italic>Cm</italic>3245 possesses a very high exo-acting activity of hydrolyzing GlcNAc dimer. These results suggest that chitinases and NAGase from SYBC-H1 both play important roles in conversion of <italic>N</italic>-acetyl chitooligosaccharides to GlcNAc, resulting in the accumulation of the final product GlcNAc. To our knowledge, this is the first report of the complete genome sequence and chitinolytic enzyme genes discovery of this strain.</p>