Localization of some phosphatases in yeast

Abstract

1. 1. The localization of some phosphatases has been studied in yeast cells that were either fragmented by shaking intact cells with glass beads or by hypotonic or isotonic disruption of protoplasts prepared from intact cells. 2. 2. The non-specific acid phosphatase with optimum activity at pH between 3 and 4 was shown to occur in the cell wall of commercial baker's yeast. As some substrates of the enzyme can only enter that part of the cell volume corresponding to the cell wall and the activity is not increased by freezing and thawing the yeast, it was concluded that all the enzyme is located here. 3. 3. The highly specific α-glycerophosphatase is entirely present in the unstructured cytoplasm of a 17-h culture of Saccharomyces carlsbergensis (No. 74). 4. 4. S. carlsbergensis (No. 74) contains only one non-specific alkaline phosphatase. The distribution depends upon the age of the culture: In a culture aged 17 h two-thirds of the enzyme is bound to particles sedimenting from 3000 × g to 100 000 × g, and one-third is soluble. In a culture aged 24 h 70–85% of the enzyme is found in the soluble fraction, and only a small amount is particle bound.