THE METABOLISM OF THE ERYTHROCYTE: XIII. ENZYME ACTIVITY IN THE RETICULOCYTE

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Abstract
To ascertain the changes that occur in the activity of the enzymes of the reticulocyte during its manifestations to the normocyte (adult erythrocyte), blood specimens were taken from rabbits in which a severe anemia and a pronounced reticulosis (50-90% reticulocyte count) had been produced by giving the animals subcutaneous injections of acetylphenyl-hydrazine. Succinic dehydrogenase, cytochrome oxidase, and DPN-ase were confined to the insoluble fraction of the cells, glucose-6-phosphate dehydrogenase and pyrophosphatase to the soluble fraction (stroma-free hemolyzate.) Isocitric, lactic, and malic dehydrogenases, fumarase, aconitase, and hexokinase were present in both fractions. The activity of fumarase, hexokinase, and pyrophosphatase was much lower in the normocyte than in the reticulocyte while that of the isocitric, lactic, and malic dehydrogenases and of DPN-ase was of the same order in both types of cell. Aliquots of blood specimens were kept at 37[degree]C for 12 hours and the activity of numerous enzymes was followed at 2-hourly.intervals. The enzymes which are more active in the reticulocyte decrease in activity with decrease in reticulocyte count. Succinic dehydrogenase, cytochrome oxidase, and aconitase are absent from the normocyte. The significance of these changes with respect to reticulocyte maturation is discussed. Exposure of hemolyzates of blood specimens to ribonuclease to destroy any ribonucleic acid present, did not alter the activity of any of the enzymes tested. The DPN-ase of the reticulocyte, as of the normocyte, was a nucleosidase which splits the linkage between nicotinamide and ribose.