Evidence for a postsynthetic proteolytic transformation of human erythrocyte pyruvate kinase into L‐type enzyme

The relationship between liver (L-type) and erythrocyte pyruvate kinase remains a subject of discussion. It has been previously demonstrated that these enzymes are kinetically [ 1,2] and immunologltally [3-51 related. In some cases liver (Ltype) pyruvate kinase from patients with hereditary erythrocyte pyruvate kinase deficiency was shown to be defective [2,6-81. Erythrocyte and L-type enzymes, however, can be distinguished by their electrophoretic mobilities [2,9] . Some authors [9] have suggested that erythrocyte enzyme might be a hybrid between Ltype and non-L-type subunits: the demonstration by Peterson et al. [lo] that, by sodium dodecylsulphate-acrylamlde gel electrophoresis, erythrocyte pyruvate kinase was resolved into two distinct bands with similar mobility, supported this assumption. We have purified erythrocyte enzyme by a new method, previously reported [ Ill. The crucial step of this purification procedure was an affinity chromatography on a bluedextran Sepharose 4 B column, with selective elution by fructose-l ,6diphosphate. Under some conditions, red cell pyruvate kinase was eluted from the blue-dextran Sepharose column in two peaks. The purpose of this work was to study the nature of those two molecular forms of the erythrocyte enzyme in relation to the L-type enzyme from liver.