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Cutting the Gordian Knot: Identifiability of anaplerotic reactions in Corynebacterium glutamicum by means of 13 C‐metabolic flux analysis
Author(s) -
Kappelmann Jannick,
Wiechert Wolfgang,
Noack Stephan
Publication year - 2016
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.25833
Subject(s) - corynebacterium glutamicum , knot (papermaking) , flux (metallurgy) , identifiability , chemistry , corynebacterium , biochemistry , biology , bacteria , mathematics , genetics , materials science , gene , organic chemistry , statistics , composite material
ABSTRACT Corynebacterium glutamicum is the major workhorse for the microbial production of several amino and organic acids. As long as these derive from tricarboxylic acid cycle intermediates, the activity of anaplerotic reactions is pivotal for a high biosynthetic yield. To determine single anaplerotic activities 13 C‐Metabolic Flux Analysis ( 13 C‐MFA) has been extensively used for C. glutamicum , however with different network topologies, inconsistent or poorly determined anaplerotic reaction rates. Therefore, in this study we set out to investigate whether a focused isotopomer model of the anaplerotic node can at all admit a unique solution for all fluxes. By analyzing different scenarios of active anaplerotic reactions, we show in full generality that for C. glutamicum only certain anaplerotic deletion mutants allow to uniquely determine the anaplerotic fluxes from 13 C‐isotopomer data. We stress that the result of this analysis for different assumptions on active enzymes is directly transferable to other compartment‐free organisms. Our results demonstrate that there exist biologically relevant metabolic network topologies for which the flux distribution cannot be inferred by classical 13 C‐MFA. Biotechnol. Bioeng. 2016;113: 661–674. © 2015 Wiley Periodicals, Inc.