Recombinant expression, purification, and biochemical characterization of chondroitinase ABC II from Proteus vulgaris

Chondroitin lyases (or chondroitinases) are a family of enzymes that depolymerize chondroitin sulfate (CS) and dermatan sulfate (DS) galactosaminoglycans, which have gained prominence as important players in central nervous system biology. Two distinct chondroitinase ABC enzymes, cABCI and cABCII, were identified in Proteus vulgaris. Recently, cABCI was cloned, recombinantly expressed, and extensively characterized structurally and biochemically. This study focuses on recombinant expression, purification, biochemical characterization, and understanding the structure-function relationship of cABCII. The biochemical parameters for optimal activity and kinetic parameters associated with processing of various CS and DS substrates were determined. The profile of products formed by action of cABCII on different substrates was compared with product profile of cABCI. A homology-based structural model of cABCII and its complexes with CS oligosaccharides was constructed. This structural model provided molecular insights into the experimentally observed differences in the product profile of cABCII as compared with that of cABCI. The critical active site residues involved in the catalytic activity of cABCII identified based on the structural model were validated using site-directed mutagenesis and kinetic characterization of the mutants. The development of such a contaminant-free cABCII enzyme provides additional tools to decode the biologically important structure-function relationship of CS and DS galactosaminoglycans and offers novel therapeutic strategies for recovery after central nervous system injury.