Amount and properties of uptake forms in preparations of alpha-mannosidase from pig kidney

alpha-Mannosidase (alpha-D-mannoside mannohydrolase, EC 3.2.1.24) from pig kidney has been shown to exist in multiple forms differing in their capability to be endocytosed by alpha-mannosidase deficient cultured cells. A method is presented to evaluate the amount of "uptake" forms in different preparations of the enzyme. Preparations with different rates of uptake were shown to contain different amount of "uptake" forms and "non-uptake" forms. The content of "uptake" forms in a preparation was identical with that of enzyme molecules bearing a phosphorylated carbohydrate group necessary for the recognition by cell surface receptors.