Biochemical properties of a novel and highly thermostable bacterial α-carbonic anhydrase from Sulfurihydrogenibium yellowstonense YO3AOP1

Abstract

A new carbonic anhydrase (CA, EC 4.2.1.1) from the thermophilic bacterium Sulfurihydrogenibium yellowstonense YO3AOP1 was identified and characterized. The bacterial carbonic anhydrase gene was expressed in Escherichia coli yielding an active enzyme, which was purified in large amounts. The recombinant protein (SspCA) was found to belong to the α-CA class and displays esterase activity. The kinetic parameters were determined by using CO₂ and p-nitrophenylacetate (p-NpA) as substrates. The bacterial enzyme presented specific activity comparable to that of bovine carbonic anhydrase (bCA II) but it showed biochemical properties never observed for the mammalian enzyme. The thermophilic enzyme, in fact, was endowed with high thermostability and with unaltered residual activity after prolonged exposure to heat up to 100°C. SspCA and the bovine carbonic anhydrase (bCA II) were immobilized within a polyurethane (PU) foam. The immobilized bacterial enzyme was found to be active and stable at 100°C up to 50 h.

Keywords::

• Metalloenzyme
• α-class enzyme
• esterase
• CO₂ hydrase
• protein purification

Acknowledgments

The authors thank Dr. Claudiu T. Supuran (University of Florence) for helpful discussions concerning this work.

Declaration of interest: This research was financed by a grant of the “Accordo di Programma CNR-MSE.”