TABLE 3.

Comparison of experimental and predicted mass isotopomer distributions during growth of wild-type G. sulfurreducens on acetate-fumarate medium containing unlabeled acetate and 30% [13C]fumarate

Amino acid and mass isotopomeraExperimental mass isotopomer distributionbPredicted MDVc
Threonine pathwayCitramalate pathwayBoth pathways
Aspartate
    M+00.70930.69080.68900.6983
    M+100.02560.02340.0250
    M+20.29070.28360.28750.2765
    M+3000.00010.0002
Isoleucine
    M+00.86620.67580.86440.8619
    M+10.02630.03600.03720.0393
    M+20.09670.28190.09340.0952
    M+30.00870.00470.00250.0020
    M+40.00200.00170.00250.0016
    M+50.0001000
Leucine
    M+00.89370.86550.85970.9196
    M+10.04090.03720.04670.0407
    M+20.04150.09240.08850.0383
    M+30.00520.00250.00290.001
    M+40.0010.00250.00230.0004
    M+50.0177000
Total errord 0.37840.12710.0622
  • a The unlabeled molecule is shown as M+0, and numbers above zero correspond to the number of additional mass units (13C atoms).

  • b Experimental values are averages of two fragments for each amino acid, both missing the carboxy-terminal carbon atom. The mass isotopomer distributions for these two fragments were the averages of three derivatizations performed on extracts prepared from pooled duplicate cultures.

  • c MDVs were calculated by running the optimization routine assuming each pathway separately, and then allowing the optimization routine to select the best-fitting ratio between them.

  • d Errors are the sum of squared differences between predicted and experimental values for aspartate, isoleucine, and leucine fragments.