RT Journal Article
SR Electronic
T1 Design principles of autocatalytic cycles constrain enzyme kinetics and force low substrate saturation at flux branch points
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 074641
DO 10.1101/074641
A1 Uri Barenholz
A1 Dan Davidi
A1 Ed Reznik
A1 Yinon Bar-On
A1 Niv Antonovsky
A1 Elad Noor
A1 Ron Milo
YR 2017
UL http://biorxiv.org/content/early/2017/01/02/074641.abstract
AB A set of chemical reactions that require a metabolite to synthesize more of that metabolite is an autocatalytic cycle. Here we show that most of the reactions in the core of central carbon metabolism are part of compact autocatalytic cycles. Such metabolic designs must meet specific conditions to support stable fluxes, hence avoiding depletion of intermediate metabolites. As such, they are subjected to constraints that may seem counter-intuitive: the enzymes of branch reactions out of the cycle must be overexpressed and the affinity of these enzymes to their substrates must be relatively weak. We use recent quantitative proteomics and fluxomics measurements to show that the above conditions hold for functioning cycles in central carbon metabolism of E.coli. This work demonstrates that the topology of a metabolic network can shape kinetic parameters of enzymes and lead to seemingly wasteful enzyme usage.