Reversible hydration of carbon dioxide. H(+) + hydrogencarbonate = CO2 + H2O Inhibited by acetazolamide. Expressed in liver and muscle. Repressed by 3,3',4,4',5-pentachlorobiphenyl (PenCB) and 3-methylchlantherene (3MC). S-thiolated both by thiol-disulfide exchange with glutathione disulfide and by oxyradical-initiated S-thiolation with reduced glutathione. S-glutathionylated in hepatocytes under oxidative stress. Expressed at much higher levels in the adipocytes of lean Zucker rats than in obese Zucker rats. Expression is higher is the adipocytes of male Zucker rats than in female Zucker rats. Belongs to the alpha-carbonic anhydrase family.