Subcellular Distribution of Human Leukocytic Cathepsins

I N STUDYING certain properties of peripheral leukocytic cathepsins in health and disease,1’2 we found that whole fresh cells contained two pH optima, 3.5 and 8.5, when denatured hemoglobin was used as a substrate.3 Mounter and Atiyeh,4 employing casein as a substrate for extracts of leukocytes, noted optima at pH 3.0, 5.5, and 8.0. Haschen and Krug,5’#{176} using denatured hemoglobin as substrate, reported the presence of proteases active at pH 3.5 and 7.5 as well as seven different peptidases, in normal and leukemic blood. Since we considered it important to know the catheptic activity in the isolated leukocytes in order to compare leukemic cells with their normal counterparts, we separated the lymphocytes from the granulocytes7 and measured their respective catheptic activities at pH 3.5 and 8.5. We found that the lymphocytes displayed more catheptic activity per cell at pH 3.5 than the granulocytes, and the granulocytes more activity than the lymphocytes at pH 8.5. It then became apparent that at pH 3.5, lymphatic leukemia cells were considerably lower than normal lymphocytes and myelogenous leukemic and polycythemic cells much higher than normal granulocytes (polycythemic blood frequently contained as much as 85 per cent granulocytes ) . On the other hand, at pH 8.5, both types of leukemic cells were less active than their normal counterparts and polycythemic cells are approximately the same as normal granulocytes. These observations indicated that the differences noted in the leukemic cells were not due to a preponderance of one type of cell but rather to inherent deranged biochemical properties of the cells.2 Frei and his collaborators8 measured the catheptic activity of normal and leukemic leukocytes at pH 7.4, with casein as substrate. They found normal granulocytes to be almost four times as active as normal lymphocytes, cells of acute myelogenous leukemia less active, cells of chronic myelogenous leukemia more active than normal granulocytes and all lymphatic leukemia cells less active than normal lymphocytes.