Purified pyruvate kinases type M 2 from unfertilized hen's egg are substrates of protein kinase C

To characterize pyruvate kinase isoenzymes from cells with the capability to proliferate, this enzyme was purified from yolk and vitelline membrane of unfertilized hen's egg. Pyruvate kinase type M 2 from vitelline membrane was obtained in a homogeneous form after a 1150‐fold purification to a specific enzymatic activity of 450 μmol · min −1 · mg −1 . It was saturated half‐maximally with phosph oenol pyruvate at K PPrv 0.5 = 0.36 mM phosph oenol pyruvate and was activated by fructose 1,6‐bisphosphate and L‐serine at suboptimal substrate concentrations. After 11000‐fold purification to a specific enzymatic activity of 60 μmol min −1 · mg −1 , the pyruvate kinase isoenzymes type M 2 ( K PPrv 0.5 = 0.32 mM) and M 1 ( K PPrv 0.5 = 0.04 mM) were obtained from the yolk substance. Kinetic differences were noted between the pyruvate kinase type‐M 2 isoenzymes from vitelline membrane and yolk. A comparison of the amino acid composition of the purified pyruvate kinase isoenzymes from hen's egg revealed that all isoenzymes were related to pyruvate kinase type M 1 from chicken breast muscle. The M 2 ‐type isoenzyme from vitelline membrane was related to the M 2 ‐type isoenzyme from chicken tumors, but was not related to the M 2 ‐type pyruvate kinase from chicken lung or liver. Protein kinase C from chicken oviduct phosphorylated in vitro both pyruvate kinase M 2 isoenzymes from the unfertilized hen's egg preferably at serine and less at threonine residues. Pyruvate kinase type M 1 from egg yolk was a weak substrate of protein kinase C. An activation of pyruvate kinase type M 2 from vitelline membrane was observed at suboptimal concentrations of phosph oenol pyruvate under the conditions of phosphorylation, in the presence of phosphatidylserine.