An investigation of the effect of vitamin c on the enzyme carbonic anhydrase

Vitamin C (ascorbic acid); in humans are unable to synthesize, serving as a reducing agent, showing antioxidant properties and that a water-soluble vitamin. However, the specific concentrations of the ascorbic acid are known in aqueous fluid of human eye.Carbonic anhydrase (CA) is a metalloenzyme that contains zinc ion. It catalyses that the reversible hydration of carbon dioxide to yield bicarbonate. Human eye tissue contains CA I, CA II and CA IV isoenzymes. Glaucoma is an eye disease which characterized by high intraocular pressure that causes eventually blindness. Carbonic anhydrase inhibitors have been used for treatment of glaucoma, because of their decrease higher intraocular pressure which occurs with excessive secretion of aqueous humor.In this study, the inhibitory effect of vitamin C on carbonic anhydrase isoenzymes that is hCA I and hCA II were investigated. First of all, hCA I and hCA II isoenzymes were respectively purified from human erythrocytes with affinity chromatography and purity of the enzymes was checked with SDS-PAGE electrophoresis. Later, the inhibitory effects of the different concentrations of vitamin C solutions on hCA I and hCA II isoenzymes were determined. To determine inhibitory effect of vitamin C, the hydratase and esterase activities of carbonic anhydrase enzyme were measured. According to the results, %Activity-[I] graphics were drawn and the IC50 values were calculated. The Ki constants were calculated from Lineweaver-Burk graphics.Finally, Any inhibitory effects of the different concentrations of vitamin C solutions were not showed on hydratase activities of hCA I and hCA II isoenzymes. But these solutions were showed inhibitory effects on the esterase activities of hCA I and hCA II isoenzymes. The IC50 values of compounds for esterase activity are 0,96?103-0,07?103 ?M for hCA I and 0,23?103-0,06?103 ?M for hCA II, respectively. The Ki values of these inhibitors are 0,97?102-0,43?102 ?M for hCA I and 1,2?102-0,36?102 ?M for hCA II, respectively.Keywords: Vitamin C, Carbonic Anhydrase, Inhibition, IC50 Values.