Characterization of functionally active immobilized carbonic anhydrase purified from sheep blood lysates

Abstract

Carbonic anhydrase (CA) catalyzes the reversible reaction of hydration of CO2 to bicarbonate and the dehydration of bicarbonate back to CO2. Sequestration of CO2 from industrial processes or breathing air may require a large amount of highly active and stable CA. Therefore, the objectives of the present study were to purify large amounts of CA from a cheap and easily accessible source of the enzyme and to characterize the enzymatic and kinetic properties of soluble and immobilized enzyme. We recovered 80% of pure enzyme with a specific activity of 4870EU/mg protein in a single step using sheep blood lysates from slaughter house waste products and CA specific inhibitor affinity chromatography. Since affinity pure CA showed both anhydrase and esterase activities, we measured the esterase activities for enzymology. The Michaelis–Menten constant, KM, pH optimum, activation energy, and thermal stability of soluble enzymes were 8×10−2M, 7.3 pH, 7.3kcal/mol and 70°C, respectively.The immobilization of the enzyme to Affigel-10 was very efficient and 83% of purified enzyme was immobilized. The immobilized enzyme showed a KM of 5×10−2M and activation energy of 8.9kcal/mol, suggesting a better preference of substrate for immobilized enzyme in comparison to soluble enzyme. In contrast to soluble enzyme, immobilized enzyme showed relatively higher activity at pH 6–8. From these results, we concluded that a shift in pH profile toward acidic pH is due to modification of lysine residues involved in the immobilization process. The immobilized enzyme was stable at higher temperatures and showed highest activity at 80°C. The activity of immobilized enzyme in a flow reactor at 0.5–2.2ml/min flow rate was unaffected. Collectively, results from the present study suggested the application of blood lysate waste from animal slaughterhouses for purification of homogeneous enzyme for CO2 capture in a flow reactor.