Experimental and Computational Study of Hyaluronidase Interactions with Glycosaminoglycans and their Ligands

Covalent conjugation of hyaluronidase with copolymeric glycosaminoglycans (GAG, heparin and dermatan sulfate) considerably inactivates the enzyme, while conjugation with polymeric GAG (chondroitin sulfate and hyaluronan) improves its stability. These effects are associated with structural differences of these GAG caused by C-5 epimerization of glucuronic and iduronic acid residues and different effects of (alpha[1 - 4] and alpha[1 - 3] relative to beta[1 - 4] and beta[1 - 3]) glycosidic bonds. Pronounced effects of galactose C-4 epimers (in comparison with glucose) and disaccharide mixture (lactose, cellobiose, maltose) on endoglycosidase activity of hyaluronidase emphasize the importance of its diversified multi-contact microenvironment. For a better understanding of the mechanisms regulating hyaluronidase activity, molecular docking and molecular dynamics were chosen. Stabilization effect of chondroitin ligands on heat inactivation of hyaluronidase was demonstrated. An increase in denaturation temperature by 10-15 degrees C hampers blocking of the active site entrance and prevents the enzyme inactivation. Enzyme-GAG interactions were examined by molecular docking with molecular dynamic elaboration. Gradual chemical modification of hyaluronidase was based on the calculated sequence of preferential binding of GAG. Theoretically, covalent binding of chondroitin sulfate trimers at cs7 or cs7, cs1 and cs5 on the enzyme surface provides complete protection against heparin inhibition. Computational investigation of hyaluronidase microenvironment and interactions which limit the enzyme activity allows identification of the best GAG regulators of hyaluronidase endoglycosidase activity and their experimental verification.