A Cl-/HCO-3-ATPase in the gills of Carassius auratus. Its inhibition by thiocyanate.
An ATPase is demonstrated in plasma membrane fractions of goldfish gills. This enzyme is stimulated by Cl- and HCO-3, inhibited by SCN-. Biochemical characterization shows that HCO-3 stimulation (Km = 2.5 mequiv./l) is specifically inhibited in a competitive fashion by SCN- (Ki = 0.25 mequiv./l). This residual Mg2+-dependent activity is weakly affected by SCN-. In the microsomal fraction chloride stimulation of the enzyme occurs in the presence of HCO-3 (Km for chloride = 1 mequiv/l); no stimulation is observed in the absence of HCO-3. Thiocyanate exhibits a mixed type of inhibition (Ki = 0.06 mequiv./l) towards the Cl- stimulation of the enzyme. Bicarbonate-dependent ATPase from the mitochondrial fraction is stimulated by Cl-, but this enzyme has a relatively weak affinity for this substrate (Km = 14 mequiv./l).
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology; D002712:Chlorides / Q000494:pharmacology*; D005880:Gills / Q000201:enzymology*; D006054:Goldfish; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D011092:Polyethylene Glycols / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013861:Thiocyanates / Q000494:pharmacology*
D001639:Bicarbonates; D002712:Chlorides; D013861:Thiocyanates; D011092:Polyethylene Glycols; D012964:Sodium; D000251:Adenosine Triphosphatases; D008274:Magnesium; D011188:Potassium