IMMUNOLOGICAL STUDY OF AGE-RELATED LOSS OF ACTIVITY OF 6 ENZYMES IN RED-CELLS FROM NEWBORN-INFANTS AND ADULTS-EVIDENCE FOR A FETAL TYPE OF ERYTHROCYTE PHOSPHOFRUCTOKINASE

Blood from 10 normal healthy adults and cord blood from 8 healthy full term infants were infiltrated through a mixture sulfoethylethycellulose-Sephadex G 25 in order to eliminate the platelets and the leukocytes. Then the erythrocytes were fractionated into young and old cells by centrifugation in microhematocrit tubes. The enzyme activity and the immunologic reactivity of glucose phosphate isomerase [GPI] (EC.5.3.1.9), phosphoglycerate kinase [PGK] (EC.2.7.2.3), pyruvate kinase [PK] (EC.2.7.1.40), glucose 6-phosphate dehydrogenase [G6PD] (EC.1.1.1.49) and 6-phosphogluconate dehydrogenase [6GPD] (EC.1.1.1.44) were measured in every fraction. As previously reported, the enzyme activities were far higher in cord blood than in adult blood red cells. The age-related loss of enzyme activity was similar in cord and adult blood. The decrease of the enzyme activity of GPI and PGK in old cells was singly associated with a lowered concentration of the enzyme-related antigen. The age-related decrease of the enzyme activity of PK, G6PD, and 6PGD was associated with a lowered concentration of the enzyme-related antigen and a lowered molecular specific activity (i.e., a lowered ratio of enzyme activity to enzyme-related antigen concentration). This phenomenon was especially marked for PK, which had a molecular specific activity in old cells that was 68% of that in young cells. Phosphofructokinase [PFK] had a lower enzyme activity in cord blood erythrocytes than in adult blood erythrocytes; the difference was especially important in old cells from infants in which PFK activity was 53% of that in old cells from adults. PFK from old cells of full term infants and from unfractionated cells from 2 premature infants (21 and 32 wk of gestation) was less neutralized by anti-muscle PFK serum and more inhibited by ATP than the enzyme from adult blood erythrocytes.