Comparative binding of albumin and -glucuronidase by rat liver microsomes

Rat liver microsomes, free of lysosomal β-glucuronidase, were subjected to sonication. Under the experimental conditions used, 95 % of the microsomal β-glucuronidase activity was solubilized while only 11 % of the albumin was released in the soluble fraction. The results indicate that microsomal β-glucuronidase is not contained in the cisternae of the microsomal vesicles but is attached to the membranes by bonds that are broken by sonication before the membranes are disrupted.