Modification of pyruvate kinase activity by proteins from chicken liver

Purification and characterization of human meningioma M2-type pyruvate kinase

The M2-type pyruvate kinase was purified from human meningioma by ammonium sulfate precipitation, followed by ion exchange and affinity chromatography. The specific activity of the purified enzyme was 33.4 U/mg with a yield of 6.5%. The enzyme gave a single band with 63,000 +/- 2000 Da upon SDS polyacrylamide gel electrophoresis. On cellulose acetate electrophoresis zymograms, the purified enzyme (M2) showed a single band, while crude extracts gave two broad bands corresponding to pyruvate kinase isozymes. The pI value of purified enzyme was found to be 6.9. With phosphoenol pyruvate as substrate the purified enzyme showed sigmoidal kinetics, while in the presence of 0.6 mM fructose 1,6-diphosphate as modulator it gave a hyperbolic saturation curve with a Km value of 0.53 mM.

Modification of pyruvate kinase activity by proteins from chicken liver

The partial purification of a protein fraction inhibiting pyruvate kinase isoenzymes is described. The fraction was isolated from the (NH4)2SO4 step of the purification procedure for pyruvate kinase isoenzymes from chicken liver (Eigenbrodt, E. & Schoner, W. (1977) Hoppe-Seyler's Z. Physiol. Chem. 358, 1033-1046) by extraction with 1N NaOH, acidification to pH 3, ethanol precipitation and chromatography of the supernatant on DEAE-cellulose. The inhibitor fraction was further purified by disc gel electrophoresis using a gel gradient from 10 to 25%; this procedure separated activating proteins from the inhibitor fraction. The inhibitor fraction inhibited the pyruvate kinase isoenzymes from chicken in the sequence of decreasing effect: M2 greater than L greater than M1. The inhibition was due to a decrease in the affinity for phosphoenolpyruvate. The inhibitor is stable against heating for 5 min in 1% sodium dodecyl sulfate at 100 degrees C; it is destroyed by pepsin digestion. The inhibitor fraction could be purified further only by dodecyl sulfate gel electrophoresis. This resulted in the separation of 2 inhibitors (Mr = 33,500 +/- 8500 and ca. 5000), an activator (Mr = 15,100 +/- 5200), and an unidentified protein (Mr = 27,000).