Jana Wolf

Humboldt-University, Institute of Biology, Theoretical Biophysics,
Invalidenstr. 42, 10115 Berlin, Germany

Concerning glycolytic oscillations in yeast the question arises, which
effect the coupling between the cells has on the dynamics of the system.
This is studied on the basis of a model, which describes the anaerobic
glycolytic pathway rather detailed. Intercellular coupling is included
by transmembrane diffusion of acetaldehyde, since it has been
hypothesized that this substance mediates the interaction.

For a single cell the model may show stationary or oscillatory behaviour
depending on the kinetic parameters. The oscillatory dynamics correspond
to experimental data with respect to metabolite concentrations and phase
shifts between cellular metabolites. The inclusion of the coupling
between cells leads to a variety of dynamical modes, such as synchronous
oscillations and different kinds of asynchronous behaviour. The
corresponding parameter regions have been identified by a bifurcation
analysis.

The intercellular coupling in synchronized cell populations is
investigated by calculating the phase responses to acetaldehyde pulses.
Moreover, simulations are performed with respect to the synchronization
of two subpopulations that are oscillating out of phase before mixing.
The effect of the various processes on the synchronization is
characterized quantitatively. While continuous exchange of acetaldehyde
might synchronize the oscillations for appropriate sets of parameter
values, the calculated synchronization time is longer than observed
experimentally.

It is concluded either that, in addition to the transmembrane exchange
of acetaldehyde, other processes may contribute to intercellular
coupling, or that internal regulatory feedback plays a role in the
acceleration of the synchronization.