Determination of catalase activity in samples treated with [ZnCl2(isopropylamine)2]: a novel zinc complex that slows down the decay in activity of catalase extracts

Abstract

Reaction of ZnCl₂ with an excess of isopropylamine ligand in water gives [ZnCl₂(isopropylamine)₂]. This novel zinc complex has been characterized by elemental analysis and ¹H-NMR. Interestingly, we have found that [ZnCl₂(isopropylamine)₂] markedly retards the decay in activity of catalase extracts. In fact, catalase extracts (0.075 mg of protein ml⁻¹) may retain more than 80% of their initial enzymatic activity within the first 10 hours of incubation with 0.10 μM [ZnCl₂(isopropylamine)₂] while the activity of control extracts decreases to less than 50% of the initial value. Moreover, after 24 hours of treatment with [ZnCl₂(isopropylamine)₂] under the above-mentioned conditions, 70% of the initial enzymatic activity is still retained by catalase extracts while the activity of control untreated extracts drops to 17% of the initial value. On the other hand, our results show that after incubation of catalase extracts with [ZnCl₂(isopropylamine)₂] the supernatants obtained by centrifugation of the extracts contain a higher amount of active catalase than the supernatants of control untreated catalase extracts. Moreover, [ZnCl₂(isopropylamine)₂] induces precipitation of a large amount of contaminant proteins present in the catalase extracts. Altogether, these data indicate that treatment of catalase extracts with [ZnCl₂(isopropylamine)₂] both increases the pureness of catalase solutions and slows down the decay in catalase activity. We believe that [ZnCl₂(isopropylamine)₂] may be useful as a stabilizing agent for enzyme activity assays with crude catalase extracts.