PEP + ADP ------> pyruvate + ATP

The product pyruvate can be converted to acetyl CoA and can enter the TCA cycle. Under conditions where cells carry out anaerobic metabolism, the pyruvate is converted to lactate.

Erythrocytes do not have mitochondria and are thus, dependent, on glycolysis for energy. It might be expected that the a PK defect would have a particular damaging effect on erythrocytes. PK-deficient erythrocytes have impaired glycolysis and difficulty in maintaining normal levels of ATP and NAD. Most patients with PK deficiency have low red cell ATP levels. The reduced energy is probably the cause of poor maintenance of cellular integrity which accounts for the diminished life span of affected erythrocytes in severe PK deficiency.

In fact, it is now known that there are three isozymes of pyruvate kinase in human tissues. Leukocytes of patients with erythrocytes PK deficiency have normal enzyme activity . Observations of normal activity in some cells and not in others lead to the original discovery of the isozymes. Isozyme I is found in erythrocytes and liver, isozyme II in kidney, and isozyme III in liver, kidney, leukocytes, skeletal muscle, and cardiac muscle. Liver from a patient with red cell PK deficiency has deficient PK I but normal PK III. Pyruvate kinase deficiency of the red cell is transmitted as an autosomal recessive trait.

Case Study on Pyruvate Kinase Deficiency.