SYMMETRICAL MODEL OF FERMENT STRENGTH REGULATION
Symmetrical model is one of the two models, which explain the cooperative mechanism of ferment strength regulation. The symmetrical model assumes that every multimer ferment complex can exist at least in two different states with unequal quaternary structure, while all subunits have similar tertiary structure in each state. In the simplest model two states, which are in equilibrium with each other, are considered. In one of them the protein has high affinity for the substrate (R-state, from "relax"), and in the other one it has low affinity (T-state, from "tense"). The added substrate will preferably bond with R-conformers of the ferment, while its bonding with a T-conformer will result in occurrence of tension in ferment subunits, and this will cause simultaneous transfer of all subunits into the R-state (in which there no tension). In such coordinate transfer molecular symmetry of every multimer molecular is preserved. When adding more substrate, more and more molecules will transfer from T- into R-state. Such shift of equilibrium in the presence of substrate presents the positive cooperativity effect.