Differential inhibition effects of novel chromone-based sulfonamides in cytosolic carbonic anhydrase (CA-I and CA-II) and tumor associated carbonic anhydrase (CA-IX and CA-XII) isoenzymes

Carbonic anhydrases (CAs, EC 4.2.1.1) are one of the zinc enzymes which catalyze the reversible hydration of carbon dioxide to bicarbonate ion and proton. Cytosolic carbonic anhydrase isoenzyme CA-I is the most abundant enzyme in red blood cells and the other cytosolic isoenzyme CA-II is highly expressed in several organs and contributes to most important physiological processes. CA-IX and CA-XII are transmembrane tumor associated isoenzymes because their extracellular enzyme domains are highly active and their expressions are induced by hypoxia. In this preliminary study, differential in vitro inhibiton effects of twelve novel chromone-based sulfonamide derivatives were investigated for CA-I, CA-II, CA-IX and CA-XII. CA activities were determined by hydratase activity with using Stopped-Flow Instrument. According to inhibition studies of novel chromone sulfonamides, 7a and 11a compounds were most potent for tumor associated isoenzyme CA-IX. Also, 4a and 10a compounds were most potent for tumor associated isoenzyme CA-XII. These results were given with kinetic constants as CA-IX, Ki=14.26 nM, Ki=18.39 nM for compound 7a and 11a respectively. Besides, the other kinetic constants as CA-XII, Ki= 4.54 nM, Ki= 5.23 nM for 4a and 10a respectively. This study shows that 4a, 7a, 10a and 11a compounds are selective against to CA-IX and CA-XII. From this point of view these derivative compounds could prove in potential pharmaceutical applications such a new approach for the treatment in some clinical applications.