Carbonic anhydrase activity of isolated brush border and basal-lateral membranes of renal tubular cells.

Carbonic anhydrase activity was found and characterized in isolated homogeneous preparations of microvilli and basal infoldings of the rat renal tubular cells. This membrane-bound activity was about 3% of the total carbonic anhydrase activity of the renal cortex. Compared to the renal cytoplasmic soluble form, the membrane-bound enzymes had the same Km for CO2 and were equally resistant to inhibition by chloride. However, they were less inhibited by different sulfonamides. The implication of the existence of membrane-bound enzymes in the renal tubular cells is discussed.