Purification and biochemical characterization of catalase that confers protection against hydrogen peroxide induced by stressful desert environment: the Camelus Dromedarius kidney catalase

Camel is continually exposed to stressful desert environment that enhances generation of reactive oxygen species, including hydrogen peroxide (H2O2). Catalase plays an important role in detoxification of H2O2. A highly active catalase from camel kidney was purified to homogeneity, with a specific activity of 1,774,392 U/mg protein, using ion exchange and metal chelate affinity chromatography. The molecular weight of the enzyme was 268 kDa consisting of four identical subunits of 63 kDa. The enzyme showed higher optimum temperature (45 degrees C) and higher activation energy (4.37 kJ mol(-1)). The thermodynamic parameters, Delta H, Delta G and Delta S, were determined. The effect of various metal ions and chemicals on enzyme activity was investigated. K-m, V-max, k(cat) and k(cat)/K-m values for H2O2 were found to be 46 mM, 10,715,045 U/mg, 48,265,968 s(-1) and 2,966,562 s(-1 )mM(-1), respectively. Camel kidney catalase displayed higher affinity efficiency for H2O2 and can protect reduced glutathione (GSH) from oxidation by H2O2. Sodium azide was found to be a noncompetitive inhibitor of enzyme with K-i and IC50 of 17.88 mu M and 20.94 mu M, respectively. Camel catalase showed unique biochemical properties. Interestingly, camel catalase can protect molecules (GSH) and organ functions (kidney) from the toxic effects of H2O2 induced by stressful desert environment.