Purification and properties of phosphoprotein phosphatase from ox spleen

Abstract

Phosphoprotein phosphatase has been shown, for the first time, to be present in cattle tissues. Using a combination of ammonium sulfate- and acetone-fractionation procedures, a 200-fold purification of the enzyme from ox spleen with an overall yield of 20% was effected. The enzyme is a true phosphoprotein phosphatase, distinct from the acid phosphomono-esterase, since it attacked ail 3 phosphoproteins studied, but had no appreciable action on glycerophosphate or casein phospho-peptone. Opt. enzyme activity was found at pH 6.0 and at a substrate concn. corresponding to about 10 [mu] moles/ml. of casein P with 0.001 [image] thioglycollic acid as activator. Activation and inhibition studies show that sulfhydryl and amino groups are essential for enzyme activity, but no dialyzable coenzyme is required.