Some Kinetic Properties of Liver Pyruvate Kinase (Type L)

Purification, catalytic and regulatory properties of Rana ridibunda erythrocyte pyruvate kinase

Pyruvate kinase of Rana ridibunda erythrocytes is one of the regulatory enzymes of glycolysis. PK was purified about 7800-fold. The purified enzyme showed on SDS-electrophoresis three protein bands with an apparent molecular weight of between 60 and 65 kD. The enzyme is subject to activation by FDP and to inhibition by ATP. It showed Km values for PEP and ADP of 0.095 and 0.98 mM respectively. It was activated by K+, Mg2+ and Ca2+ ions whereas it was inhibited by Na+ ions. The role of PK of Rana ridibunda erythrocytes, as a key and rate controlling enzyme of the glycolytic flux is discussed.

Acquired pyruvate kinase deficiency. The effect of maleic acid upon human erythrocyte pyruvate kinase

1. Maleic acid is shown to be able to bind the thiol compound 2-mercaptoethanol. This is fully consistent with the data of Morgan and Friedman (1938). 2. Human erythrocyte pyruvate kinase dissolved and quantitated in Tris-maleate shows a loss of positive homotropic interactions, as compared to the same preparation in Tris-HCl. Hill coefficients (n) of n = 1.0-1.2 and n = 1.6-1.8 are obtained in Tris-maleate and Tris-HCl respectively. Half saturation [S] 0.5 and Vmax remain unchanged. Pyruvate kinase in Tris-maleate is slightly more stable to heating at 60 degrees C than in Tris-HCl. Incubation of the enzyme in Tris-maleate for one h with high concentrations of dithiotreitol restores the positive homotropic interactions. 3. It is proposed, that the abnormalities of the pyruvate kinase of some patients with acquired pyruvate kinase deficiency, obtained from a study in Tris-maleate, may partly be induced by the buffer itself.