Hyaluronidase isoforms from developing embryos of the camel tick Hyalomma dromedarii

Changes in hyaluronidase activity in the camel tick Hyalomma dromedarii were followed throughout embryogenesis. Peak activity of the enzyme on days 21 and 24 during development was accompanied with a complete organization of larvae before hatching on day 27. During purification of hyaluronidase to homogeneity, ion exchange chromatography lead to four forms (HAase1, 2, 3 and 4). HAase2 and HAase4 with highest purity and specific activities after chromatography on Sephacryl S-200. The apparent molecular masses of HAase2 and HAase4 were 25 and 40 kDa, respectively. HAase2 and HAase4 had the same pH optimum of 3.6 and Km values of 0.3 and 0.34 mg/mL hyaluronic acid, respectively. Cleaving activities of HAase2 and HAase4 were demonstrated in the order: hyaluronic acid > chondroitin sulphate A > chondroitin sulphate C > chondroitin sulphate mixed > chondroitin sulphate B > heparin, low M.Wt > heparin. HAase2 and HAase4 had the same temperature optimum (40 °C) with heat stability up to 40 °C. H. dromedarii HAase2 and HAase4 had broad plateau of NaCl requirement with optimum activity recorded at 0.15 and 0.3 M NaCl, respectively. HAase2 and HAase4 were inhibited by Ca2+, Fe3+, Co2+and Hg2+and enhanced by Mg2+and Mn2+.