Table II.

Influence of metabolic network structure on determination of flux estimates

Fluxes were determined by fitting isotopomer abundances and biosynthetic output estimates to a family of models differing in the extent of PPP compartmentation (Figs. 1 and 2). Each model contained a complete plastidic PPP pathway. Free fluxes that varied during the fitting procedure are indicated in boldface. Net fluxes and normalized hyperbolic transformed exchange fluxes are the global best fit estimate ± sd as determined by EstimateStat and are calculated relative to the rate of Glc uptake (set to unity). A normalized exchange flux for which sd takes the estimated value outside the permissible [0,1] range is considered indeterminate (Ind).

Flux NameFlux (Relative to Glc Uptake)
No Cytosolic PPPCytosolic Oxidative PPP Steps OnlyComplete Cytosolic PPP
Net flux
    chex10.317 ± 0.0620.191 ± 0.0830.665 ± 0.074
    chex20.241 ± 0.0620.115 ± 0.0830.365 ± 0.187
    chex30.778 ± 0.0160.786 ± 0.0210.894 ± 0.040
    phex10.049 ± 0.0670.209 ± 0.101−0.160 ± 0.090
    phex20.305 ± 0.0630.442 ± 0.0880.228 ± 0.187
    phex30.072 ± 0.0160.075 ± 0.0200.000 ± 0.040
    cppp10.372 ± 0.0280.266 ± 0.019
    cppp2a−0.224 ± 0.200
    cppp2b−0.112 ± 0.100
    cppp2c−0.112 ± 0.100
    cppp3a−0.112 ± 0.100
    cppp3b−0.112 ± 0.100
    pppp10.405 ± 0.0180.000 ± 0.0390.000 ± 0.027
    pppp2a0.138 ± 0.0060.127 ± 0.0090.204 ± 0.102
    pppp2b0.118 ± 0.0060.107 ± 0.0090.184 ± 0.102
    pppp2c0.256 ± 0.0120.234 ± 0.0180.388 ± 0.204
    pppp3a0.138 ± 0.0060.127 ± 0.0090.204 ± 0.102
    pppp3b0.138 ± 0.0060.127 ± 0.0090.204 ± 0.102
    tca10.650 ± 0.0060.661 ± 0.0090.696 ± 0.009
    tca20.650 ± 0.0060.661 ± 0.0090.696 ± 0.009
    tca30.624 ± 0.0060.635 ± 0.0090.670 ± 0.009
    tca40.572 ± 0.0060.583 ± 0.0090.618 ± 0.009
    tca50.573 ± 0.0060.584 ± 0.0090.619 ± 0.009
    ana10.241 ± 0.0040.241 ± 0.0040.243 ± 0.005
    ana20.039 ± 0.0030.040 ± 0.0040.039 ± 0.004
    ana30.026 ± 0.0010.026 ± 0.0010.029 ± 0.003
    cmex0.610 ± 0.0070.621 ± 0.0090.657 ± 0.009
    cpex0.112 ± 0.0150.109 ± 0.0190.181 ± 0.037
    gpt0.496 ± 0.0620.251 ± 0.088−0.118 ± 0.082
    tpt/ppt0.540 ± 0.1240.801 ± 0.1710.523 ± 0.471
    xpt0.603 ± 0.309
Normalized exchange flux
    chex10.990 ± 0.1020.990 ± 0.1080.423 ± 0.066
    chex20.682 ± 0.0550.667 ± 0.0530.803 ± 0.073
    phex10.476 ± 0.0400.475 ± 0.0540.148 ± 0.103
    cppp2a0.990 ± 0.276
    cppp2b0.320 ± 0.082
    cppp2cInd
    cppp3aInd
    cppp3b0.000 ± 0.194
    pppp2aIndIndInd
    pppp2b0.990 ± 0.1410.990 ± 0.1660.990 ± 0.588
    pppp2c0.990 ± 0.1200.990 ± 0.1150.990 ± 0.502
    pppp3aIndIndInd
    pppp3b0.268 ± 0.0390.299 ± 0.0590.252 ± 0.123
    tca50.719 ± 0.0430.719 ± 0.0430.730 ± 0.044
    gpt0.970 ± 0.0510.695 ± 0.0670.462 ± 0.096
    tpt/ppt0.227 ± 0.1400.441 ± 0.1150.000 ± 1.424
    xpt0.309 ± 0.362