Biochemical switching device: Monocyclic enzyme system

Abstract
The switching characteristics of a monocyclic enzyme system, in which two enzymes share substrates or co‐factors in a cyclic manner, such as, → X1 + B + E1A + E1 + X2 →, → X3 + A + E2B + E2 + X4 → (E1, E2 are enzymes, X1, X3 are substrates, X2, X4 are products, A, B are cofactors), were demonstrated using computer simulations. The detailed mathematical models of biochemically possible cyclic enzyme systems were built up and the effects of rate constants and the effects of initial concentrations of enzymes and cofactors on switching characteristics were discussed. The cyclic enzyme system could function as a switching circuit when the initial concentrations of enzymes or cofactors are over a certain threshold value. Based on the present results, we further discuss the dynamic characteristics of a biochemical reactor system (bioreactor) involving this cyclic enzyme system as a switching controller.