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  • Title: The kinetic properties of the ecto-ATPase of human peripheral blood lymphocytes and of chronic lymphatic leukemia cells.
    Author: Gutmann HR, Chow YM, Vessella RL, Schuetzle B, Kaplan ME.
    Journal: Blood; 1983 Nov; 62(5):1041-6. PubMed ID: 6138109.
    Abstract:
    This study examines whether the activity of the Mg2+-dependent ecto-ATPase of the surface membrane of the human lymphocyte is changed in chronic lymphocytic B-cell leukemia (CLL-B) and may be an indicator of malignant transformation. The ecto-ATPase activities of preparations consisting predominantly of T or B cells were compared to each other and to the ecto-ATPase of the CLL peripheral blood lymphocytes (PBL). The specific activities and kinetic constants of the ecto-ATPase of the cell preparations were determined with [gamma-32P] adenosine triphosphate (ATP) as substrate. B-enriched lymphocytes had nearly fourfold greater specific activity and apparent Vmax than T-enriched lymphocytes, while the Km values of both cell types showed no significant difference. The specific activities and kinetic constants of the ecto-ATPase of the CLL PBL were significantly higher than the corresponding values of PBL or of B-enriched lymphocytes. Judging from the kinetic constants the ecto-ATPase of the CLL-B lymphocyte appears to be an enzyme that is distinctly different from that of the normal B cell. On the basis of the kinetic properties, the ecto-ATPase of the B cell appears to be identical with that of the T cell. The differences in the maximal velocities of the hydrolysis of ATP by B and T cells are likely due to a greater number of enzymatic sites on the B cell.
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