Isolation and Properties of Pig Muscle Phosphorylase*

Abstract

A method for the purification and crystallization of phosphorylase [EC 2.4.1.1] b from pig muscle was described. Conversion of pig muscle phosphorylase b to phosphorylase a and crystallization of the latter form were accomplished. Pig phosphorylases b and a both appeared as a single component on ultracentrifugation. Phosphorylase b had a sedimentation coefficient of 8.5. No increase of the S value occurred upon conversion to phosphorylase a in the presence of more than 0.03 M cysteine, while at a cysteine concentration lower than 0.03 M, phosphorylase a gave heavier components. The relationship between cysteine concentration and polymerization of molecules was discussed. The presence of polymers was confirmed on disc-electrophoresis. These polymers seemed to have the activity. The pH optimum of pig phosphorylases b and a was 6.4 and 6.2 respectively. Assuming a molecular weight of 250,000, it was inferred that pig muscle phosphorylase a contained 2 moles of pyridoxal 5′-phosphate per mole of the enzyme.