Catalase from larvae of the camel tick .

Catalase plays a major role in protecting cells against toxic reactive oxygen species. Here, Catalase was purified from larvae of the camel tick and designated TLCAT. It was purified by ammonium sulfate precipitation and chromatography on DEAE-cellulose, Sephacryl S-300 and CM-cellulose columns. Gel filtration and SDS-PAGE of the purified TLCAT indicated that the protein has a native molecular weight of 120 kDa and is most likely a homodimer with a subunit of approximately 60 kDa. The Km value of TLCAT is 12 mM HO and displayed its optimum activity at pH 7.2. CaCl, MgCl, MnCl and NiCl increased the activity of TLCAT, while FeCl CoCl, CuCl and ZnCl inhibited the activity of TLCAT. Sodium azide inhibited TLCAT competitively with a Ki value of 0.28 mM. The presence of TLCAT in cells may play a role in protecting ticks against oxidative damage. This finding will contribute to our understanding of the physiology of these ectoparasites and the development of untraditional methods to control them.