Cl- -HCO3- -stimulated ATPase in intestinal mucosa of Aplysia.
The serosa negative transepithelial potential difference across Aplysia intestine is generated by a Na+-independent, active electrogenic Cl- absorptive mechanism. In an attempt to clarify the Cl- absorptive mechanism an anion-stimulated ATPase was prepared from plasma membranes from Aplysia enterocytes utilizing differential centrifugation and sucrose density gradient techniques. ATPase activity, which could be activated by either Cl- or HCO3-, was found in the plasma membrane fraction. Maximal anion-ATPase activity was achieved with either 25 mM Cl- or 25 mM HCO3-. The apparent Km for Cl- activation of the ATPase was 10.3 mM, whereas apparent Km for HCO3- was 9.7 mM. ATP was the most effective nucleotide substrate for both HCO3- and Cl- -ATPase activities, whereas optimum pH for both activities was 7.8. These enzyme activities were inhibited more than 30% by thiocyanate (10 mM). Acetazolamide and vanadate were also found to strongly inhibit both Cl- and HCO3- -ATPase activities, whereas 10 microM 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, 1 mM furosemide, or 1 mM ouabain had little or no effect. These results are consistent with the hypothesis that the active Cl- transport mechanism in Aplysia intestine could be a Cl- -HCO3- -stimulated ATPase found in the enterocyte plasma membrane.
Gerencser
G A
GA
Lee
S H
SH
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D027321:Anion Transport Proteins; D000838:Anions / Q000494:pharmacology; D001048:Aplysia / Q000378:metabolism*; D017301:Ca(2+) Mg(2+)-ATPase; D007413:Intestinal Mucosa / Q000201:enzymology*; D007700:Kinetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D027321:Anion Transport Proteins; D000838:Anions; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; C031652:anion-sensitive ATPases; D000254:Sodium-Potassium-Exchanging ATPase