The disaccharidase activity of a membrane fraction obtained from the rabbit renal cortex.

Abstract

Abstract An investigation has been made into the disaccharidase activities found in the rabbit renal cortex with particular reference to their selective solubilization by the use of proteolytic enzymes. 1. 1. A membrane fraction which carries high specific activities of the enzymes maltase and trehalase (0.14 and 0.52 μmole substrate hydrolyzed/min per mg protein) has been isolated from the rabbit renal cortex. It appears to represent brush border membrane together with its associated external coat. 2. 2. Brief treatment of this particulate material with papain releases a soluble fraction which is excluded from Sephadex G-100, and which contains 8 % of the total protein and 90 % of the total maltase activity. The specific activity of this soluble enzyme is increased by 10–20 times. Almost all (99 %) of the trehalase activity remains on the membrane. 3. 3. Treatment of the membranes with trypsin also releases a soluble fraction excluded from G-100 but in smaller yield (approx. 3 % of total protein). However, no maltase and only a trace of trehalase activity could be detected in this fraction, almost all the activities being retained in the particulate residue.