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

Abstract

1. 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. 2. Human erythrocyte pyruvate kinase dissolved and quantitated in Trismaleate 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°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. 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.