The Inhibition Kinetics of Bovine and Human Erythrocyte Carbonic Anhydrase Isozymes with Some Active Cations

Authors: Hasan ÖZDEMİR, İrfan KÜFREVİOĞLU, Barbaros NALBANTOĞLU, Nazan DEMİR, Nuri BAKAN

Abstract: In this study, the in vitro effects of some active cations on carbonic anhydrase (CA) isozymes were investigated. Bovine (BCA) and human (HCA-I and H CA-ll) isozymes were purified by affinity chromatography from bovine and human erythrocytes. In order to make the kinetic studies, esterase activities of CA isozymes were determined. By using AI{^3+}, Mn{^2+}, Sr{^2+}, Hg{^2+}, Ni{^2+}, Ca{^2+}, and Cd{^2+}ions, K _iconstants for CA isozymes were found by means of Linewear-Burk graphics. While A1{^3+} showed competitive inhibition, the others displayed noncompetitive inhibition. In addition, the inhibitor concentrations halving the enzyme activity (I{_50} values) were determined. The determined I{_50} values for BCA, HCA-I and CA-ll were fit to the obtained Ki values.

Keywords: Carbonic anhydrase, isozymes, active cations, kinetics