alpha-Galactosidase from Saccharomyces carlsbergensis. Cellular localization, and purification of the external enzyme

1. The alpha-galactosidase of Saccharomyces carlsbergensis in an inducible enzyme which is localized mainly outside the cell membrane and which is secreted into the culture medium in increasing amounts during the growth cycle. 2. The soluble form of alpha-galactosidase localized inside the cell appears to have the same characteristics as the external one, contrasting with the different forms found in the case of invertase. Although some activity is membrane-bound, this activity, when solubilized with detergent, has the same characteristics as the external form of the enzyme. 3. A procedure has been developed by which the enzyme has been purified using batch adsorption with DEAE-Sephadex and column chromatography in DEAE-Sephadex, DEAE-cellulose and Sephadex G-200, using the supernatant of a culture of Saccharomyces carlsbergensis grown in yeast/nitrogen base complemented with galactose. 4. The purified enzyme, which is homogeneous by chromatographic criteria and polyacrylamide gel electrophoresis, appears to be glycoprotein. 5. Invertase copurifies with the alpha-galactosidase but because of its lower stability, together with the fact that the synthesis of both enzymes can be controlled separately, it was possible to obtain preparations in which the contaminant activity was approximately 1%.