Immunologie Study of the Age-related Loss of Activity of Six Enzymes in the Red Cells from Newborn Infants and Adults — Evidence for a Fetal Type of Erythrocyte Phosphofructokinase

Abstract

Summary: 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 micro-hematocrit tubes. The enzyme activity and the immunologic reactivity of glucose phosphate isomerase (EC. 5.3.1.9), phosphoglycerate kinase (EC. 2.7.2.3), pyruvate kinase (EC. 2.7.1.40), glucose 6-phosphate dehydrogenase (EC. 1.1.1.49), and 6-phosphogluconate dehydrogenase (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; nevertheless, the age-related loss of enzyme activity was similar in both cord and adult blood. The decrease of the enzyme activity of glucose phosphate isomerase and phosphoglycerate kinase in old cells was singly associated with a lowered concentration of the enzyme-related antigen; by contrast, the age-related decrease of the enzyme activity of pyruvate kinase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase was associated with both 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 pyruvate kinase, which had a molecular specific activity in old cells that was 68% of that in young cells. Phosphofructokinase 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 phosphofructokinase activity was 53% of that in old cells from adults. Phosphofructokinase from old cells of full term infants and from unfractionated cells from two premature infants (21 and 32 weeks of gestation) was less neutralized by anti-muscle phosphofructokinase serum and more inhibited by ATP than the enzyme from adult blood erythrocytes. Speculation: The phenomenon of molecular aging of the enzymes in red cells could differ for every enzyme. In some cases molecular aging could lead to degradation of the molecules; these would then no longer be recognizable either by their catalytic activity or by their antigenic properties. In other cases molecular aging could be associated with the inactivation (partial or total) of some molecules which would not be changed with respect to their antigenic properties. These phenomena do not seem to differ in either cord blood or adult blood erythrocytes. The low enzyme activity of phosphofructokinase in cord blood red cells seems to be a unique feature of the “fetal” erythrocytes and seems to result from the synthesis in the fetal erythroblasts of a “fetal-type” phosphofructokinase. This fetal enzyme could be relatively deficient in the muscle-type subunit which accounts for about 50% of the activity of the normal phosphofructokinase in adult blood erythrocytes. These data could be involved in the metabolic peculiarities and in the reduced viability characterizing the fetal red blood cells.