Spontaneous biochemical oscillations are often thought to be caused
by a so-called oscillophore, a key enzyme that is the primary source of
the oscillations. In yeast glycolytic oscillations phosphofructokinase
seemed to be such an oscillophore, since removing the positive feedback
regulation on this enzyme in a core model of glycolysis, removed the oscillations
completely at any combination of kinetic parameter values.
In real glycolysis, however, more than one possible source of oscillations
has been identified. In order to quantify to which extent each enzyme contributes
to the occurrence of oscillations, we applied the principles of Metabolic
Control Analysis. We calculated the control exerted by each enzyme on the
real part and the trace of the eigenvalues of stable as well as of instable
steady states. We concluded that even in the above mentioned core model,
the control on the eigenvalues was distributed among several enzymes. In
a detailed and realistic model of yeast glycolysis most, but not all control
of the eigenvalues was shared by glucose transport, pyruvate decarboxylase
and the utilization of ATP. From these results we conclude that the concept
of an oscillophore cannot be applied to complex biochemical networks. Instead,
Metabolic Control Analysis provides an unambiguous method to determine
the importance of each enzyme for the emergence of oscillations.