Combining chitinase C and N-acetylhexosaminidase from Streptomyces coelicolor A3(2) provides an efficient way to synthesize N-acetylglucosamine from crystalline chitin.
Résumé
The enzymatic bioconversion of chitin is of considerable interest for the natural production of bioactive compounds such as chitooligosaccharides and N-acetyl-d-glucosamine (GlcNAc). Key enzymes are involved in the natural processing of chitin, hydrolyzing this abundant biopolymer to yield chitooligosaccharides with substantial value to the medicinal and biotechnological fields. In this study, chitinase C (ScChiC) from the soil bacterium and chitin decomposer Streptomyces coelicolor A3(2) was expressed, purified and characterized. We also optimized a Streptomyces lividans system generating ScChiC expression yields nearly 500-fold higher than the previously reported heterologous expression in Escherichia coli. The purified enzyme was found to be stable below 55°C for a broad range of pH values (pH 3.5-9) and exhibited high activity against chitin and chitooligosaccharides to form chitobiose (C2) as main product. Crab shell chitin hydrolysis profiles also revealed that ScChiC catalyzes the bioconversion of chitopolysaccharides through an endo-nonprocessive mode of action. When combining ScChiC with an N-acetylhexosaminidase from S. coelicolor A3(2) (ScHEX) in an assay using crude extracts and crystalline chitin as substrate, GlcNAc was generated as final product with a yield over 90% after 8h incubation. This chitin hydrolysis yield represents one of the most efficient enzyme bioconversion of chitopolysaccharides to GlcNAc characterized to date, making the S. coelicolor ScChiC-ScHEX pair a potentially suitable contender for the viable industrial production of this important bioactive compound.