Purification and characterization of aspartate aminotransferase from developing embryos of the camel tick Hyalomma dromedarii.

Aspartate transaminase (AST) activity in the camel tick Hyalomma dromedarii was followed throughout embryogenesis. During purification of AST to homogeneity, ion exchange chromatography lead to four separate forms (termed I, II, III and IV). AST II with the highest specific activity was pure after chromatography on Sephacryl S-300. The molecular mass of AST II was 52 KDa for the native enzyme, composed of one subunit of 50 KDa. AST II had a Km value of 0.67mM for a-ketoglutarate and 15.1 mM for aspartate. AST II had a pH optimum of 7.5 with heat stability up to 50 degrees C for 15 min. The enzyme was activated by MnCl2, and inhibited by CaCl2, MgCl2. NiCl2, and ZnCl2.