A Kinetic Analysis of the Uptake of Cytosine‐β‐d‐Arabinoside by Rat‐B77 Cells
- 1 April 1979
- journal article
- research article
- Published by Wiley in European Journal of Biochemistry
- Vol. 95 (2), 333-339
- https://doi.org/10.1111/j.1432-1033.1979.tb12970.x
Abstract
Cytosine-.beta.-D-arabinoside is a synthetic nucleoside which has been useful in the treatment of human leukemias. Kinetic methods were used to differentiate the tandem processes of transport and metabolic trapping during uptake of cytosine-.beta.-D-arabinoside by intact rat fibroblasts [B77 cells]. Transport across the cell membrane occurs by a carrier-mediated mechanism displaying a Km of .apprxeq. 500 .mu.M and Vmax of .apprx. 300 pmol/min per (106 cells). The subsequent metabolic trapping (phosphorylation) has a Km of .apprxeq. 15 .mu.M and Vmax of .apprxeq. 0.25 pmol/min per (106 cells). In this system, transport is rate-limiting for the 1st phase of the uptake process and phorphorylation becomes rate-limiting when intracellular concentration of labeled substrate exceeds that in the surrounding medium. The duration of the 1st phase depends on the substrate concentration.This publication has 13 references indexed in Scilit:
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