Chitin deacetylase from Colletotrichum lindemuthianum

Abstract

Publisher Summary Chitin, a β-1,4-1inked homopolymer of N-acetyl-D-glucosamine, is accompanied in the walls of various fungi by chitosan, a polymer similar to chitin by lacking the N-acetyl groups. Chitosan is most likely synthesized by partial deacetylation of the nascent chain of chitin once the latter is formed by chitin synthase from UDP-GlcNAc. After crystallization the microfibrillar chitin appears to be a relatively poor substrate for the respective enzyme chitin deacetylase. This mode of biosynthesis suggests that the chitin/chitosan complex occurring in fungal cell walls is not a mixture of the two pure polymers but is represented by chitin chains that are deacetylated to a variable degree. The question arises, why in plant pathogens of the genus Colletotrichum can high activities of chitin deacetylase be found in the culture filtrate? It appears possible that in addition to the formation of chitosan as a structural element of the cell wall, the secreted enzyme may play a role in the production of shorter chain chitosan fragments. The chitin deacetylases from M. rouxii and from C lindemuthianum are highly active on oligomers derived from chitin. Similar fragments arise by the action of endochitinases of plant or fungal origin and might represent a readily accessible substrate for a secreted chitin deacetylase.