Purification of protoplast-secreted acid phosphatase from baker's yeast. Effect on adenosine triphosphatase activity.

In order to examine acid phosphatase (EC 3.1.3.2) and ATPase (EC 3.6.1.3) activities of baker's yeast (pH optimum 3.5) a protoplast-secreted enzyme preparation was purified and some physical and chemical properties were studied. Three protein fractions containing ATPase and acid phosphatase activities, in the same ratio as the initial preparation, were separated by ion-exchange chromatography. The first fraction which had the highest protein content yielded a homogeneous preparation after Sepharose 4B chromatography and was used in further studies. An attempt to estimate molecular weight of this protein was made. Attempts to separate acid phosphatase and ATPase activities by ion-exchange chromatography, gel filtration, isoelectric focusing and sucrose density gradient centrifugation have been unsuccessful. Both activities behaved the same way to heat and urea denaturation. These results suggest that the two activities are associated with the same protein molecule.