Studies on the localization and properties of rat duodenal HCO3--ATPase with special relation to alkaline phosphatase

• Published in: Biochimica et biophysica acta Vol. 924; no. 1; pp. 159 - 166
• Main Authors: WILKES, J. M, GARNER, A, PETERS, T. J
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 16.04.1987; North-Holland
• Subjects: Adenosine Triphosphatases - metabolism; Alkaline Phosphatase - metabolism; Analytical, structural and metabolic biochemistry; Animals; Anion Transport Proteins; Biological and medical sciences; Cell Fractionation; Duodenum - enzymology; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrolases; Intestinal Mucosa - enzymology; Kinetics; Male; Microvilli - enzymology; Microvilli - ultrastructure; Rats; Rats, Inbred Strains; Alkaline phosphatase; Membrane enzyme; Vertebrata; Brush border; Mammalia; Rat; ATPase; Rodentia; Gut; Effector
• ISSN: 0006-3002; 0304-4165; 1878-2434
• DOI: 10.1016/0304-4165(87)90083-3

Brush-border membrane fractions were isolated from rat duodenum. Purity and integrity of the fraction was confirmed by electron microscopy, enzymic analysis and demonstration of Na+-dependent glucose uptake. The membranes were enriched 15-fold in alkaline phosphatase and alpha-glucosidase and 6-fold in HCO3--ATPase activities. Assays of latent activity indicated that these enzymes were predominantly localised to the external aspect of the microvillus membrane. The enzymes were solubilised and subjected to analysis by gel filtration, ion exchange and phenylboronate chromatography. No separation of alkaline phosphatase and HCO3--ATPase was obtained and it is suggested that they reflect the same enzyme activity. The apparent activation by HCO3- was investigated, and was found to be due to shifts in the pH dependency of the activity due to changes in ionic strength.