Some Anti-Inflammatory Agents Inhibit Esterase Activities of Human Carbonic Anhydrase Isoforms I and II: An In Vitro Study.

Carbonic anhydrases (CAs) are known as a drug-target enzymes. The inhibitors of the enzyme are important compounds for discovering new therapeutic agents and understanding in detail protein-drug interactions at the molecular level. For this purpose, the in vitro effects of some anti-inflammatory agents such as tenoxicam, fluorometholone acetate, and dexamethasone were investigated on esterase activity of human erythrocyte CA-I and CA-II in this study. hCA-I and hCA-II were purified by affinity chromatography with a yield of 47.25% and 87%, and a specific activity of 642.8 EU/mg proteins and 5576.9 EU/mg proteins, respectively. SDS-PAGE was performed to determine the purity of the enzymes. Inhibitory effects of the drugs on hCA-I and hCA-II were determined by spectrophotometric method. IC50 values for hCA-I and hCA-II were 0.198, 2.18, 11.7, 0.11, 17.5 and 14 μm using tenoxicam, fluorometholone acetate, and dexamethasone, respectively. For fluorometholone acetate and dexamethasone, Ki values from Lineweaver-Burk plots were obtained as 1.044 and 21.2 μm (noncompetitive) for hCA-I and 9.98 and 8.66 μm (non-competitive) for hCA-II. In conclusion, tenoxicam, fluorometholone acetate, and dexamethasone showed potent inhibitory effects on esterase activity of hCA-I and hCA-II isozymes under in vitro conditions.