β-Glucuronidase of Rat Liver Lysosomes

Previous work has established that rat liver contains several closely related forms of β-glucuronidase differing in their subcellular distribution. The present report focuses on the most abundant form, which is the major one occurring in lysosomes. This β-glucuronidase was purified 8,400-fold, to the highest specific activity thus far reported. The preparation is homogeneous by all criteria applied. It contains a relatively high content of glutamic and aspartic acids and a very low content of sulfur-containing amino acids. The enzyme has a molecular weight of approximately 280,000, the value obtained depending upon the method used for the determination. Since gel filtration in the presence of urea, or polyacrylamide gel electrophoresis under denaturing conditions, yielded results suggesting that the enzyme consists of subunits of molecular weight of approximately 75,000, the native enzyme apparently is a tetramer.