Acetylsalicylate hydrolase of rabbit gastric mucosa. Isolation and purification

Abstract

The mechanisn of hydrolysis of acetylsalicylate during absorption from the gastrointestinl tract has been investigated by identification, quantitation, and purification of a hydrolase from gastric mucosal homogenates. The hydrolase was found to be a soluble, cytosolic enzyme with a pH optimum in the slightly alkaline range, pH 8.6 Acetylsalicylate hydrolase activity was purified from the 100,000 g supernatant fraction by differential (NH4)2SO4 fractionation followed by DEAE-cellulose ion-exchange chromatography and Sephadex or Sephacryl gel filtration. The activity could also be fractionated on hydroxylapatite. The Sephadex-purified fraction containing peak enzyme activity gave a single protein band on SDS-polyacrylamide gel electrophoresis. The molecular weight of the acetylsalicylate hydrolase was 66,400 based on SDS-polyacrylamide gel electrophoresis of the Sephadex-purified enzyme and 59,000 based on gel filtration. By use of the technique described, acetylsalicylate hydrolase can be purified over 100-fold to a specific activity of 10.6 mumol . mg-1 . min-1.