MODELLING OF KINETICS OF?ENZYME-CATALYSED REACTIONS PROCEEDING
WITH PARTICIPATION OF ACTIVATORS APPLIED TO ATP HYDROLYSIS BY Mg2+-ATPase
Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
Theoretical investigation of the model of reaction of ATP hydrolysis by “basal” Mg2+-ATPase has been carried out. It has been assumed that during the reaction each of three reacting substances (Mg2+, АТР, enzyme) can combine into complexes in couples with other participants of this process. Then the third component can associate with formed complexes producing the ternary complex of enzyme–activator–substrate. Such approach allowed to take into account all possible interactions in the chosen system, to investigate overall process in detail avoiding any simplifications and to find such peculiar properties of the process which will allow to understand the reaction mechanism and to explain observed experimental data. All possible pathways of the ATP hydrolysis process have been examined separately and as a whole. It is shown that if the reaction proceeds via two or three possible pathways then maximums are observed on plots of initial reaction rate on concentration ATP or magnesium. In addition maximums are also observed when enzyme concentration is increased. It is qualitatively new result that does not follow from the existing theories. The obtained results permit to explain some experimental data of ATP hydrolysis, active ion transport and some other reactions in a new fashion. The studied model and obtained results may be applied to another enzyme-catalysed reactions which proceed in the activator presence.
Key words: kinetics of enzyme-catalysed reactions, enzyme-catalysed ATP hydrolysis, Mg2+-dependence “basal” ATPase, reaction mechanism, reaction inhibition, mathematical modelling.
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© The Ukrainian Biochemical Journal