Studies on casein. 2. The action of phosphatases on caseins and low-molecular-weight phosphates.

1. An improved method for the preparation of phosphoprotein phosphatase from ox spleen is described. The enzyme was purified 60-fold with a yield of 21 %. 2. The enzyme preparation was free from proteolytic activity and had no action on fl-glycerol phosphate. 3. The enzyme was active on caseins, phenyl phosphate and inorganic pyrophosphate. Hence it cannot be described as a specific phosphoprotein phosphatase. 4. The pH optimum with caseins and phenyl phosphate was about pH 5-5. 5. The enzyme was stable over a wide range of pH and at temperatures below 700.