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. David Goldman

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39 Citations (Scopus)

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

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Ehrlich Tumor Carcinoma
Stereoisomerism
Carrier transport
Isomers
Tumors
Carbon
Cells
Methotrexate
Aminopterin
Folic Acid Antagonists
Folic Acid
Membranes
Kinetics
Substrates
5-methyltetrahydrofolate

ASJC Scopus subject areas

  • Biochemistry

Cite this

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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.",
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T1 - Lack of stereospecificity at carbon 6 of methyltetrahydrofolate transport in Ehrlich ascites tumor cells. Carrier-mediated transport of both stereoisomers.

AU - White, J. C.

AU - Bailey, B. D.

AU - Goldman, I. David

PY - 1978/1/10

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N2 - 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.

AB - 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.

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