[Phosphoprotein phosphatase of the myocardium. Isolation of individual molecular forms and their regulation]

Individual molecular forms of phosphoprotein phosphatase (PPase) and their inhibitors of the protein nature were isolated from rat heart muscle by means of column chromatography on DEAE Sephadex A-50. All the three fractions of PPase were capable to dephosphorylate casein but did not affect pyrophosphate. PPase I dephosphorylated trimethaphosphate or casein. The enzyme molecular forms were different from each other by the value of specific activity and sensitivity to heat treatment. Two protein inhibitors eluted by buffers of different ionic strength - 0.2 M and 1.6 M - were identified. One of them was inactivated during heat treatment (95 degrees 5 min), while the second inhibitor maintained completely its activity in these conditions.