[Cathepsin, phosphoprotein-phosphatase and acid phosphatase in the soluble fraction of the cattle brain cortex: purification and properties (author's transl)].

Cattle brain cortex was homogenised in 0, 29 mol/1 sucrose and centrifuged at 101 000 X g. The supernatant contains the majority of 3 enzymes participating in protein turnover: cathepsin (EC 3.4.4.23), phosphoprotein phosphatase (EC 3.1.3.16) and acid phosphatase (EC 3.1.3.2). They were separated by chromatography on Sephadex G 200 in neutral buffer. The cathepsin was purified up to 380 fold by gel filtration on Sephadex and column electrophoresis. The pH optimum of cathepsin was 5.7. At 37 degrees C no decrease of activity was measurable during 30 min. The Km was found to be 2.75 mg/ml Casein Hammarsten. The molecular weight by gel filtration and exclusion-gel electrophoresis was about 45 000, corresponding to the cathepsin from human liver (Barrett, A.J. (1970) Biochem. J. 117, 601-607). The sedimentation constant 3.0 S20,W is comparable with the values of proteinase of different origin, and the composition is similar with respect to the high proportion of acidic amino acids. The phosphoprotein phosphatase can be further purified by chromatography on hydroxyapatite and by column electrophoresis. The pH optimum of phosphoprotein phosphatase was about pH 5.5. At 45 degrees C no decrease of activity was measurable during 20 min; the Km was 1.43 mg/ml casein isoelectric. The pH optimum of acid phosphatase was about 5.6. At 54 degrees C NO DECREASE OF ACTIVITY WAs measurable during 30 min; the Km was 2 mumol/1 for Sodium phenolphthalein diphosphate. All three enzymes slowly lost their activity during several weeks at - 4 degrees C, apparently by self digestion in the cold.