Abstract
Cells of B lymphocyte lineage (non-E-rosetting B lymphocytes from peripheral blood or tonsils and different B lymphoblastoid cell lines) showed the presence of very active ectonucleotidase sites on their external surface. Thus, B cells are able to metabolize extracellular ATP in extracellular pathway via AMP→ADP→AMP→adenosine. Since adenosine is not produced during intracellular ATP degradation, the degradation of extracellular ATP may be the only source of adenosine production in lymphocytes. The expression of ectoATPase, ectoADPase and ectoAMPase seems to be closely associated with B cell development. EctoATPase and ectoADPase activities increase continuously during B cell maturation(early preB, late preB, mature B cells), whereas ectoAMPase reaches maximal activity in late preB cells. Extracellular nucleotide catabolism seems to have low specificity with comparable degradation rate of dATP, GTP, dGTP and CTP. Extracellular ATP degradation is stimulated by Mg2+ but not by Ca2+. These ectoenzymes are not released from cell surface to extracellular space. In contrast to B cells, T lymphocytes (E rosettlng lymphocytes from peripheral blood or tonsils were unable to degrade extracellular nucleotides. These results showed significant difference between extracellular and intracellular ATP catabolism. Intracellular ATP degradation proceeds exclusively via AMP deamination, whereas extracellular via AMP dephosphorylation resulting in adenosine formation.
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Barankiewicz, J., Dosch, HM. & Cohen, A. 7 EXTRACELLULAR NUCLEOTIDE METABOLISM AS THE MAJOR SOURCE OF ADENOSINE IN HUMAN LYMPHOCYTES. Pediatr Res 24, 112 (1988). https://doi.org/10.1203/00006450-198807000-00031
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DOI: https://doi.org/10.1203/00006450-198807000-00031