Structure and function of enzymes acting on chitin and chitosan

Abstract

Enzymatic conversions of chitin and its soluble, partially deacetylated derivative chitosan are of great interest. Firstly, chitin metabolism is an important process in fungi, insects and crustaceans. Secondly, such enzymatic conversions may be used to transform an abundant biomass to useful products such as bioactive chitooligosaccharides. Enzymes acting on chitin and chitosan are abundant in nature. Here we review current knowledge on the structure and function of enzymes involved in the conversion of these polymeric substrates: chitinases (glycoside hydrolase families 18 & 19), chitosanases (glycoside hydrolase families 8, 46, 75 & 80) and chitin deacetylases (carbohydrate esterase family 4).

Flavobacterium johnsoniae Chitinase ChiA Is Required for Chitin Utilization and Is Secreted by the Type IX Secretion System

“…Chitinases have catalytic glycoside hydrolase domains belonging to families 18 (GH18) and 19 (GH19) (35). The F. johnsoniae genome encodes five predicted chitinases with such domains (3).…”

“…S6 and S7 in the supplemental material). The two GH18 domains of F. johnsoniae ChiA exhibit little similarity to each other, but each has the signature active-site sequence (DXXDXDXE) that is characteristic of GH18 chitinases (35). B. circulans chiA1 and chiD are adjacent on the genome, and the protein products presumably work together to digest chitin (44).…”

“…In addition to their catalytic domains, many bacterial chitinases have carbohydrate-binding modules (CBMs) belonging to family 5 or 12 (35). Examination of proteins encoded by the F. johnsoniae genome revealed the complete absence of such domains, as presented in the Carbohydrate Active enZYmes (CAZY) database (http://www.cazy.org/) (45,46).…”

A Review of the Applications of Chitin and Its Derivatives in Agriculture to Modify Plant-Microbial Interactions and Improve Crop Yields

“…Chitinases, chitosanases, chitin deacetylases and proteases [16] from natural sources have been isolated and trialed to develop environmentally friendly chitin and chitosan production [17], as has lactic acid fermentation methods [18].…”

Uncoupling chitosanase production from chitosan

“…A wide diversity of exo-and endo-hydrolases acting on chitin and/or chitosan, differing by their mechanisms of hydrolysis, substrate recognition and cleavage specificity is now described in the literature. 3,[5][6][7] Enzymatic methods also have the advantage requiring only well accessible biotechnological equipment and, being less energy-consuming and yielding biodegradable waste are regarded as "green technologies". Therefore there is a growing interest in the development of inexpensive but well characterized enzymatic tools for the hydrolysis of chitosan into LMWC or CHOS.…”