Purification of carbonic anhydrase from dog erythrocytes and investigation of in vitro inhibition by various compounds

The enzyme carbonic anhydrase ( E. C. 4.2.1.1) has a stimulatory effect on glaucoma, an eye disease that has a risk to dogs, which are models for the human eye disease, that is similar to that in humans. In this study, some sulfonamide derivatives, 2-(3-cyclohexene-1-carbamido)-1,3,4-thiadiazole-5-sulfonamide (CCTS), 4( 3-cyclohexene-1-carbamido) methyl-benzenesulfonamide (CCBS), 2-(9-octadecenoylamido)-1,3,4-thiadiazole-5-sulfonamide( ODTS), 2-(4,7,10- trioxa-tetradecanoylamido)-1,3,4-thiadiazole-5-sulfonamide (TDTS), and 2-(8-methoxycoumarine3- carbamido)-1,3,4-thiadiazole-5-sulfonamide (MCTS), as well as some anionic compounds (perchlorate and chloride) and existing medicines (dorzolamide-HCl, gentamicine sulphate, tropicamide, and procaine-HCl) were assayed for their inhibition of dog carbonic anhydrase ( dCA), which was purified from erythrocytes on an affinity gel of L-tyrosinesulfonamideSepharose 4B. ODTS showed the highest potency amongst the synthetic compounds with IC50 value 1.18 X 10(25) M. Amongst the medicines tested, only dorzolamide showed inhibition with IC50 value 5.05 X 10(24) M. Procaine and tropicamide actually showed an activatory effect, whereas gentamicine sulfate had no significant effect. The inhibitory effects of anionic compounds such as perchlorate and chloride were also investigated; whereas perchlorate showed inhibition, chloride did not.