Erythrocytic proteases: preferential degradation of alpha hemoglobin chains

Proteolytic activity against native hemoglobin polypeptide chains is demonstrated, under strictly physiological conditions, in human reticulocytes of both normal subjects and individuals suffering from a variety of pathologic conditions involving erythrocytes, including beta-thalassemia. Two thirds of the activity are found in the cytoplasm and the remainder of it is associated with the reticulocyte membrane. That this proteolytic activity is due to contamination by WBC is excluded. The activity preferentially degrades the alpha-hemoglobin chains. An increase in this substrate within the erythroid cells, as observed in beta-thalassemia, does not enhance proteolysis. Protease inhibitors produce a variable decrease in proteolysis. None inhibit completely, thus showing that several enzymes, with different specificities, are involved.