A kinetic inhibition mechanism for maintenance
Tolla, C., Kooijman, S. A. L. M., Poggiale, J.-C. 2007.
A kinetic inhibition mechanism for maintenance.
J. Theor. Biol. 244: 576 - 587
Abstract
To fulfil their maintenance costs, most species use mobile pools
of metabolites (reserve) in favourable conditions, but can also use
less mobile pools (structure) under food-limiting conditions. While the
Marr-Pirt model always pays maintenance costs from structure, the
presence of reserve inhibits the use of structure for maintenance
purposes. The standard Dynamic Energy Budget (DEB) model captures
this by simply supplementing all costs that could not be paid from
reserve with structure. This is less realistic at the biochemical
level, and involves a sudden use of structure that can complicate the
analysis of the model properties. We here propose a new inhibition
formulation for the preferential use of reserve above structure in
maintenance that avoids sudden changes in the metabolites use. It is
based on the application of the DEB theory for synthesizing units,
which can easily become rather complex for demand processes, such as
the maintenance. We found, however, a simple explicit expression for
the use of reserve and structure for maintenance purposes and compared
the numerical behaviour with that of the Marr-Pirt model in
oscillating conditions, by using parameters values from a fit of the
models to data on yeasts in a batch culture. We conclude that our
model can better handle variable environments. This new inhibition
formulation has a wide applicability in modelling metabolic processes.