Cloning, purification and characterization of a novel GH46 family chitosanase, Csn-CAP, from Staphylococcus capitis

A novel chitosanase gene, designated can-cap, was cloned from Staphylococcus capitis with codon optimization and functionally expressed in Escherichia colt M15. The recombinant enzyme Csn-CAP, which belongs to the GH46 family, consists of 342 amino acids, which includes a 35-amino acid signal peptide. The mature protein was purified to homogeneity using Ni-NTA affinity chromatography, and the molecular mass of the purified enzyme was estimated to be similar to 35 kDa by SDS-PAGE. Csn-CAP displayed a maximal activity at 30 degrees C and pH 7 and a weak alkaline solution could inhibit its activity harshly. The enzyme was cold-adapted and exhibited 86% of its maximal activity at 20 degrees C. The level of enzymatic activity was enhanced by some bivalent metal cations, such as Zn2+, Cu2+ and especially Mn2+ , which could enhance the activity more than twofold at a 5 mM concentration. The enzyme exhibited strict substrate specificity for chitosan solution, colloidal chitosan and powdery chitosan, but it could not hydrolyze colloidal chitin or carboxymethylcellulose. The thin-layer chromatography result showed that Csn-CAP exhibited an endo-type cleavage pattern and hydrolyzed chitosan to yield mainly (GlcN)(2) and (GlcN)(3). Thus, the novel characteristics of the chitosanase Csn-CAP make it a potential candidate for oligosaccharide production-based industries.