Purification of a heat-stable chitin deacetylase from Aspergillus nidulans and its role in cell wall degradation

Abstract

An extracellular chitin deacetylase activity has been purified to homogeneity from autolyzed cultures of Aspergillus nidulans. This enzyme is an acidic glycoprotein with a pI of 2.75 and a 28% (wt/wt) carbohydrate content. The apparent M(r) of the enzyme estimated by SDS/PAGE and Superose 12 (f.p.l.c.) was around 27,000. The enzyme had an optimum pH at 7.0 and was stable in the pH range 4.0-7.5. Its optimum temperature of reaction was 50 degrees C, and it was stable from 30 degrees to 100 degrees C after 1 h of preincubation. The enzyme hydrolyzed glycol chitin and oligomers of N-acetylglucosamine and to a lesser extent chitin, colloidal chitin, carboxymethylchitin, and an alpha-1-->3, 1-->6-N-acetylgalactosamine-galactan among other substances with amido groups, but the enzyme did not hydrolyze peptide bonds. The role of this enzyme could be deacetylation of chitin oligosaccharides during autolysis, after action of endochitinase on cell walls.