The isoenzymes of pyruvate kinase in normal, hypothyroid and dysmature rats.

An electrophoretic study was made of the isozymes of pyruvate kinase (PK) in various adult and foetal tissues, normal or pathological (hypothyroid or dysmature as the result of retardation of intra-uterine growth) rats. The simultaneous kinetic study of PK with and without fructose diphosphate (FDP) showed that retardation of the maturation of the tissues revealed the presence of the M2 isozyme (PK III) longer than the normal foetal age. The increase of negative charges, observed in relation to age, may be the result of structural changes in the enzyme molecule which are yet to be resolved. The variations of relative electrophoretic mobility, and the reactivation of the isozyme by FDP suggest that there is a repression of the synthesis of certain isozymes in normal adult organs.