Lack of stereospecificity at carbon 6 of methyltetrahydrofolate transport in Ehrlich ascites tumor cells. Carrier-mediated transport of both stereoisomers.

J. C. White, B. D. Bailey, I. D. Goldman

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

Nonlabeled and tritiated stereoisomers of 5-methyltetrahydrofolate were prepared and were both shown to be substrates for the high affinity H4 folate cofactor membrane transport carrier in Ehrlich ascites tumor cells. Both the enzymically active form and the isomer having the opposite configuration at carbon 6 inhibited the influx of enzymically synthesized (+)-5-methyltetrahydrofolate, methotrexate, and aminopterin. When added to the media of cells preloaded with methotrexate, both isomers stimulated a net efflux of the antifolate from the cell. Influx of the natural and unnatural isomers followed Michaelis-Menten kinetics with comparable Km values. Each isomer competitively inhibited influx of the other.

Original languageEnglish (US)
Pages (from-to)242-245
Number of pages4
JournalJournal of Biological Chemistry
Volume253
Issue number1
StatePublished - Jan 10 1978
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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