α-Amylase from developing embryos of the camel tick Hyalomma dromedarii

alpha-Amylase activity in the camel tick Hyalomma dromedarii was followed throughout embryogenesis. During purification of alpha-amylase III to homogeneity, ion exchange chromatography lead to four separate forms (termed I, II, III and IV). alpha-Amylase III with the highest specific activity was pure after chromatography on Sephacryl S-300. The molecular mass of alpha-amylase III was 106 kDa for the native enzyme, composed of two subunits of 43 and 66 kDa, respectively. alpha-Amylase had a value of 10 mg starch/ml. Varying alpha-amylase activity was detected when supplied with various substrates. alpha-Amylase III had a temperature optimum at 40 degrees C with heat stability up to 50 degrees C, and a pH optimum of 7.0. The enzyme activity was activated by CaCl2, MgCl2 and NaNO3, but not activated by NaCl, p-CMB, N-ethylmaleimide and iodoacetamide. EDTA and beta-mercaptoethanol strongly inhibited activity. (C) 2000 Elsevier Science Inc. All rights reserved.