AMINO ACID ACTIVATING ENZYMES IN RED BLOOD CELLS OF NORMAL, ANEMIC AND POLYCYTHEMIC SUBJECTS*

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Abstract
Human whole blood hemolysates were found t6 contain amino acid activating enzymes (AAAE) as determined by amino acid dependent exchange of P32 labelled pyrophosphate with adenosine triphosphate (ATP). Out of 18 natural amino acids tested, tryptophan showed the highest activity. Mg ions were found to be essential. The product of the exchange reaction was identified as ATP labelled in the two terminal phosphate groups. Factors influencing the reaction rate, such as amino acid concentration and pH optimum, were determined. The bulk of AAAE was present in the red blood cells (RBC), while leukocytes showed the highest specific activity. There was no correlation between the AAAE content and the osmotic fragility of the RBC. Hemolysates from patients with macrocytic and microcytic anemias showed higher AAAE content than hemolysates from normal subjects. On the other hand, hemolysates from polycythemia vera patients exhibited a significant decrease in AAAE activity. These deviations from normal tended to improve parallel with the hematologic improvement.