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Allosteric control of pyrimidine transport in Hymenolepis diminuta: an unusual kinetic isotope effect

Published online by Cambridge University Press:  06 April 2009

G. L. Uglem ,
R. K. Dupre  and
J. P. Harley
G. L. Uglem
Affiliation:
Physiology Group, School of Biological Sciences, University of Kentucky, Lexington, Kentucky40506
R. K. Dupre
Affiliation:
Physiology Group, School of Biological Sciences, University of Kentucky, Lexington, Kentucky40506
J. P. Harley
Affiliation:
Physiology Group, School of Biological Sciences, University of Kentucky, Lexington, Kentucky40506
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Summary

A thymine–uracil transport system is present in the plasma membrane brush-border of the tapeworm, Hymenolepis diminuta. The relation between initial uptake and substrate concentration of either thymine or uracil was sigmoidal when 2-14C-labelled substrates were used. In contrast, absorption kinetics of methy 1-14C- and 3H-labelled substrates were hyperbolic. Since there was no metabolism of the labelled substrates during the incubation period, these differences indicate that the sigmoidal kinetics of pyrimidine transport in this organism is an isotope effect associated with the presence of the 14C label at the 2 position in the pyrimidine ring.

Type
Research Article
Information
Parasitology , Volume 87 , Issue 2 , October 1983 , pp. 289 - 293
Copyright
Copyright © Cambridge University Press 1983

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References

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