Pyruvate kinase isozymes in man

Abstract

Anti human M₂ type and anti human L type pyruvate kinase sera allowed us to distinguish two groups of pyruvate kinase in man. Erythrocyte and liver (L type) enzymes on the one hand were inhibited by anti L and not at all by anti M₂ serum; pyruvate kinase from all the other tissues on the other hand were inhibited by anti M₂ and not at all by anti L serum. This latter group represent the M type pyruvate kinase isozymes. The M type isozymes have been studied by electrofocusing in thin layer acrylamideampholine gel. In adult tissues 4 types of isozymes were found, designated, from acid to alkaline pH, as M₂ (predominant form in spleen, leukocytes, lung...), M₃, M₄ and M₁ (predominant form in muscle and brain). In foetal tissues an extra band M₂, called M₂f, more anodic than M₂, was added to the previously described isozymes. Except in brain (in which the isozymes M₂, M₃, M₄ and M₁ were found), the most anodic bands (M₂f, M₂ and M₃) were predominant in all the foetal tissues. The isozymes M₂f and M₂ seem therefore to be the original M type pyruvate kinase forms from which the other isozymes issue. The rate of each isozyme seems to depend on tissue factors characterizing the state of differentiation of some tissues, as indicated by the ability of adult muscle extracts to change the isozymes M₂ and M₃ into more cathodic forms.