Purification and molecular properties of bovine heart pyruvate kinase

A rapid method is presented for the purification of pyruvate kinase (ATP : pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from bovine heart. The enzyme obtained is homogeneous by criteria of sodium dodecyl sulphate polyacrylamide electrophoresis and ultracentrifugation and has a specific activity of 260 units/mg. It is a tetramer of 220 000 daltons and S020,w = 10.0 S and possesses no free amino-terminal residue. The amino acid composition is similar to that of the M1 isozyme of rabbit and bovine skeletal muscle. The enzyme is subject to polymerisation to a hexamer of the basic tetramer. The polymeric species has a molecular weight of 1320 000, is promoted at low ionic strength and is undetectable at ionic strength greater than 0.2 by either sedimentation equilibrium or sedimentation velocity measurements. The polymerisation is independent of temperature in the range 5--20degrees C implying that charge interactions rather than apolar interactions are responsible for the process.