  The minimal 3-state scheme of kinetic cooperativity of monomeric enzymes is
subjected to detailed analysis. The rigorous criteria of positive cooperativity
and its sigmoidal version are established in terms of the system parameters
(rate constants). It is shown that the cooperativity extent is especially
sensitive to the rates and direction of the exchange between conformational
states of the free enzyme. However, no necessity of the "kinetic resonance"
(or, moreover, its generality claimed recently) for enhancing cooperativity is
revealed. Overall, while the minimal 3-state model serves well for qualitative
understanding the origin of kinetic cooperativity, it is hardly suitable for
quantitative describing reactions of real enzymes, as it is shown with the case
of glucokinase.
