In vitro conversion of leucine to valine: configurational assignment of [5-13C]leucines

Chiral (2S)-[5-13C]leucine was obtained from Escherichia coli deficient in the synthesis of acetolactate when cultures were supplemented with (RS)-[2-13CH3]acetolactate. The carbon-13 nuclear magnetic resonance spectrum showed one strong peak with a chemical shift of 21.4 ppm relative to tetramethyl...

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Bibliographic Details
Published in:Biochemistry (Easton) 1981-09, Vol.20 (19), p.5609-5611
Main Authors: Sylvester, Steven R, Lan, Suey Y, Stevens, Carl M
Format: Article
Language:English
Subjects:
Carbon Isotopes
Escherichia coli - metabolism
Isomerism
Lactates - metabolism
Leucine - metabolism
Molecular Conformation
Valine - biosynthesis
Valine - chemical synthesis
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Summary:Chiral (2S)-[5-13C]leucine was obtained from Escherichia coli deficient in the synthesis of acetolactate when cultures were supplemented with (RS)-[2-13CH3]acetolactate. The carbon-13 nuclear magnetic resonance spectrum showed one strong peak with a chemical shift of 21.4 ppm relative to tetramethylsilane [Sylvester, S. R., & Stevens, C. M. (1979) Biochemistry 18, 4529-4531]. Silver picolinate oxidation of the labeled leucine gave isovaleric acid which was then brominated at the alpha position to give (2RS)-2-bromo[3-13CH3]-isovaleric acid (2-bromo-3-[13C]methylbutanoic acid). Aminolysis afforded (2RS)-[4-13C]valine which was treated with D-amino acid oxidase in the presence of catalase. The final product was identified as (2S,3S)-[4-13C]valine by the specificity of D-amino acid oxidase, by amino acid analysis, and by the persistence of a strong signal at gamma 17.8 in the carbon-13 magnetic resonance spectrum. These results establish the absolute configuration of the biosynthetic leucine to be (2S,4S)-[5-13C]leucine.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00522a039