A FETAL ISOZYME OF PHOSPHOFRUCTOKINASE IN NEWBORN ERYTHROCYTES

Abstract

Phosphofructokinase (PFK) exists in isozyme forms in various human tissues. Erythrocytes of newborns have a relative PFK deficiency and an altered rate of glycolysis. PFK in the newborn also shows increased in-vivo lability. Experiments were designed to elucidate the differences between adult and newborn erythrocyte PFK. The purified enzymes from human muscle and liver were separated by chromatography on DEAE-Sephadex A-25 columns equilibrated with 0.1M Tris-PO4 pH 8.0, and elution with a salt gradient. Human muscle and liver PFK eluted as widely separated sharp peaks. Adult erythrocyte PFK (from either crude herolysates or from purified preparations) eluted as 8 single broad peak in a position intermediate between those of the liver and muscle isozymes. Hemolysates from cord blood, examined by this technique, were found to consist of two clearly separated PFK peaks: one chromatographically indistinguishable from adult erythrocyte PFK, and a second peak chromatographically indistinguishable from liver PFK. These data demonstrate that in fetal erythrocytes there is an isozyme presumably identical with liver PFK isozyme, which is probably responsible for the relative deficiency of PFK in newborn erythrocytes.