Looking into a highly thermostable and efficient recombinant manganese-catalase from Geobacillusthermopakistaniensis

Catalases, heme or non-heme, are catalysts that decompose hydrogen peroxide. Among them, non-heme or manganese-catalases have been studied from limited organisms. We report here heterologous production of a manganese-catalase, Cat-IIGt, previously annotated as a hypothetical protein, from a thermophilic bacterium Geobacillus thermopakistaniensis. Recombinant Cat-IIGt, produced as inactive inclusion bodies in Escherichia coli, was solubilized and refolded into a soluble and highly active form. Sequence homology, absorption spectra, resistance to sodium azide inhibition and activation by Mn2+ indicated that it was a manganese-catalase. Metal analysis revealed the presence of ∼2 Mn2+ and ∼2 Ca2+ per subunit of Cat-IIGt. Recombinant Cat-IIGt exhibited highest activity at pH 10.0 and 70°C. The enzyme was highly active with a specific activity of 40,529 μmol min−1 mg−1. The apparent Km and kcat values were 75 mM and 1.5 × 104 s−1 subunit−1, respectively. Recombinant Cat-IIGt was highly thermostable with a half-life of 30 min at 100°C. The structural attributes of Cat-IIGt, including the metal and substrate binding residues, were predicted by homology modeling and molecular docking studies. High activity and thermostability and alkaline nature make Cat-IIGt a potential candidate for textile and paper processing industries.