title: Impact of transamination reactions and protein turnover on labeling dynamics in (13)C-labeling experiments.
abstract: A dynamic model describing carbon atom transitions in the central metabolism of Saccharomyces cerevisiae is used to investigate the influence of transamination reactions and protein turnover on the transient behavior of (13)C-labeling chemostat experiments. The simulations performed suggest that carbon exchange due to transamination and protein turnover can significantly increase the required time needed for metabolites in the TCA cycle to reach isotopic steady state, which is in agreement with published experimental observations. On the other hand, transamination and protein turnover will speed-up the net rate of incorporation of labeled carbon into some free and protein-bound amino acids. The simulation results indicate that the pattern of labeled carbon incorporation into amino acids obtained from biomass hydrolysate shows significant deviation from the commonly assumed first-order kinetics behavior until after three residence times. These observations suggest that greater caution should be used while also pointing to new opportunities in the design and interpretation of (13)C-labeling experiments.
authors.affiliation: Center for Microbial Biotechnology, BioCentrum-DTU, Technical University of Denmark, Building 223, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Grotkjaer
authors.forename: Mats
authors.initials: M
authors.lastname: Akesson
authors.forename: Bjarke
authors.initials: B
authors.lastname: Christensen
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Gombert
authors.forename: Jens
authors.initials: J
authors.lastname: Nielsen
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism*; D003198:Computer Simulation; D007553:Isotope Labeling / Q000379:methods; D008954:Models, Biological; D012440:Saccharomyces / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D029701:Saccharomyces cerevisiae Proteins