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

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-II, previously annotated as a hypothetical protein, from a thermophilic bacterium Geobacillus thermopakistaniensis. Recombinant Cat-II, 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 Mn indicated that it was a manganese-catalase. Metal analysis revealed the presence of ∼2 Mn and ∼2 Ca per subunit of Cat-II. Recombinant Cat-II exhibited highest activity at pH 10.0 and 70°C. The enzyme was highly active with a specific activity of 40,529 μmol min mg. The apparent K and k values were 75 mM and 1.5 × 10 s subunit, respectively. Recombinant Cat-II was highly thermostable with a half-life of 30 min at 100°C. The structural attributes of Cat-II 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-II a potential candidate for textile and paper processing industries.