Chitosanase

Chitosanase (EC 3.2.1.132) is an enzyme with systematic name chitosan N-acetylglucosaminohydrolase. This enzyme catalyses the following chemical reaction

Endohydrolysis of beta-(1->4)-linkages between D-glucosamine residues (GlcN-GlcN) in a partly acetylated chitosan

A whole spectrum of chitosanases are known.

Promiscuity

Chitosanases can be divided into four classes by the extent of their enzyme promiscuity:

Cleaves GlcNAc-GlcN and GlcN-GlcN;
Cleaves only GlcN-GlcN;
Cleaves GlcN-GlcNAc and GlcN-GlcN;
Cleaves a wide variety of β-glycosidic bonds except GlcNAc-GlcNAc (one that cleaves GlcNAc-GlcNAc would be instead considered a promiscuous endo-chitinase).

Under the CAZy classification of glycoside hydrolases, chitosanase activity mostly occurs in GH5, GH7, GH8, GH46, GH75, and GH80.

GH5 is a very large family. Some promiscuous enzymes in this family digest both carboxymethyl cellulose (CMC) [or cellulose] and chitosan.
GH7 is where most cellulases and cellulose 1,4-beta-cellobiosidases reside. A few cellulases/cellobiosidases in this family are additionally able to digest chitosan. No pure chitosanases have been identified in this family.
Most of GH8 is promiscuous. Hydrolyzable substrates in addition to chitosan may include CMC, cellulose, lichenan, and (unspecified) β-glucan.
GH46 is mostly specific to chitosan due to a conserved highly electronegative substrate-binding cleft, but one example that also digests cellulose has been found.
GH75 and GH80 are only known to be specific.

↑ Fenton DM, Eveleigh DE (1981). "Purification and mode of action of a chitosanase from Penicillium islandicum". J. Gen. Microbiol. 126: 151–165. doi:10.1099/00221287-126-1-151.
↑ Saito J, Kita A, Higuchi Y, Nagata Y, Ando A, Miki K (October 1999). "Crystal structure of chitosanase from Bacillus circulans MH-K1 at 1.6-A resolution and its substrate recognition mechanism". The Journal of Biological Chemistry. 274 (43): 30818–25. doi:10.1074/jbc.274.43.30818. PMID 10521473.
↑ Izume M, Nagae S, Kawagishi H, Mitsutomi M, Ohtakara A (March 1992). "Action pattern of Bacillus sp. no. 7-M chitosanase on partially N-acetylated chitosan". Bioscience, Biotechnology, and Biochemistry. 56 (3): 448–53. doi:10.1271/bbb.56.448. PMID 1368330.
↑ Marcotte EM, Monzingo AF, Ernst SR, Brzezinski R, Robertus JD (February 1996). "X-ray structure of an anti-fungal chitosanase from streptomyces N174". Nature Structural Biology. 3 (2): 155–62. doi:10.1038/nsb0296-155. PMID 8564542.
1 2 3 4 5 6 7 Su, H; Sun, J; Jia, Z; Zhao, H; Mao, X (November 2022). "Insights into promiscuous chitosanases: the known and the unknown". Applied Microbiology and Biotechnology. 106 (21): 6887–6898. doi:10.1007/s00253-022-12198-1. PMID 36178516.

Chitosanase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Diffusion-limited enzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)