[Enzyme inactivation in the reaction process. Regulatory role].

Some peculiarities of regulation of the enzymatic reaction involving enzyme inactivation in an open system were studied. The steady- and non-steady-state behaviour of the system upon the perturbing influence of various substrate concentrations was investigated. The steady-state responses of the system involving enzyme inactivation in the course of the reaction were compared to those for the known mechanisms directed at stabilization of the product concentration, such as competitive and incompetitive allosteric inhibition and enzyme inactivation by the reaction product. Two unique properties of the open system involving the enzyme inactivation in the course of the reaction were revealed: (1) The system is capable of maintaining an absolutely constant level of steady-state concentration of the reaction product at variable steady-state concentration of the substrate. (2) At high perturbing deviations of substrate concentrations, the non-steady response of equal amplitude is evoked; the amplitude of deviations in the product concentrations ceases to depend on the deviations in the substrate concentration. The role of regulatory influences in the mechanisms of synthesis and the effects of prostaglandins, essential regulators of the majority of physiological functions, are discussed.