We have developed two Escherichia coli strains for the production of specifically labeled amino acids suitable for high resolution nuclear magnetic resonance experiments. The 13C atoms from the enriched carbon sources, [1-13C]lactate, [1,4-13C2]succinate, and [1-13C]-acetate, are incorporated into the amino acids producing multilabeled molecules with relatively few instances of adjacent enriched carbons. This greatly simplifies the resultant spectra as compared to the extensively spin-coupled spectra of uniformly enriched samples. No isotopic enrichment was found at carbon positions expected to be unenriched by consideration of the major biosynthetic pathways. Utilizing 90% enriched precursors, most positions were enriched to approximately 85% except for those positions derived from acetate and those affected by the carbon interchange of the pentose phosphate shunt. In both of these cases, the enrichment level fell to 70%. The only result enrichment at the delta-methyl carbon of isoleucine. For the bacterial strain in question, the main pathway of isoleucine biosynthesis appears not to be from threonine but from an alternate precursor, possibly glutamate.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - Feb 10 1982|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology