Decreased L system amino acid transport and decreased gamma-glutamyl transpeptidase are independent processes in human chronic lymphocytic leukemia B-lymphocytes.
The L system of amino acid transport is markedly diminished in chronic lymphocytic leukemia (CLL) B-lymphocytes, with a maximal velocity less than 15% that of normal B-lymphocytes. Another membrane-associated function, the activity of the ectoenzyme, gamma-glutamyl transpeptidase (GGT), is diminished in CLL B-cells to 30% that of normal B-cells. In addition to its transpeptidase activity, a role for GGT has been postulated in the transport of amino acids. In the present report, the possible relationship of these two physiologic functions CLL B-cells was studied. The L system transport defect in CLL is restored by phorbol ester-induced cell maturation; following incubation with 0.15 microM tetradecanoyl phorbol acetate (TPA) for 17 hours, the L system initial velocity showed a 20-fold increase. In contrast, there was no significant effect on GGT activity with cell maturation. Furthermore, an antibody which diminished GGT activity by 50% in lymphoid cells did not inhibit L system transport. Thus, the impaired L system amino acid transport and GGT activity appear to be independent processes in CLL B-cells.
Woodlock
T J
TJ
Department of Medicine, University of Rochester School of Medicine, New York 14642.
Brown
R
R
Mani
M
M
Pompeo
L
L
Hoffman
H
H
Segel
G B
GB
Silber
R
R
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D000906:Antibodies; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D001692:Biological Transport; D002454:Cell Differentiation / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007668:Kidney / Q000201:enzymology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
D000596:Amino Acids; D000906:Antibodies; D005723:gamma-Glutamyltransferase; D013755:Tetradecanoylphorbol Acetate