Chitosanase () 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.
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