Taketoshi Hideshima

Nonlinear oscillatory reaction of catalase induced by gradual entry of substrate

Characteristic oscillatory reactions were observed when hydrogen peroxide migrated through semipermeable membrane into a solution of catalase. Measurements were made with DO and an mV meter. Oscillation clearly occurred in the range between 25 degrees C and 37 degrees C and between pH 6.0 and pH 7.6. It was also shown that a driving force for the permeation of H2O2, which was the cause of the oscillations, was a deviation from its equilibrium concentration. We made simulations for oscillatory reactions on the basis of these findings. The result indicated that considering the evaporation of O2 was necessary in order to interpret the oscillatory reactions of catalase in addition to the slow entry of substrate caused by deviation from the equilibrium concentration. The fact that oscillations arise by using this method may provide an important insight into the study of enzyme reactions mediated by membranes in living systems, because many enzyme reactions take place with the mediation of a biomembrane.

Oscillatory reaction of alcohol dehydrogenase in an oil/water system

With the use of an oil/water system, oscillatory reactions of an enzyme have been demonstrated. This reaction system has been conceived as an example of the metabolic oscillations of living cells. When a substrate (ethanol) in the oil phase of toluene or chloroform slowly migrated into the aqueous phase containing alcohol dehydrogenase and NAD+, oscillations were observed in the concentration of NADH produced. The gradual entry of substrate into the aqueous phase was essential for the oscillatory reactions to occur. A possible mechanism to account for the appearance of oscillatory reactions of enzymes is proposed, which differs from that presented previously.

Simulation of an oscillatory reaction of alcohol dehydrogenase in an oi l⧸water system

With numerical analysis of the enzyme-catalyzed reaction in the so called ordered bi-bi mechanism and the model presented by Theorell and Chance (Acta Chem. Scand. 5 (1951) 1127) for alcohol dehydrogenase, oscillations of the concentrations of coenzyme and intermediate complex were obtained on gradual entry of substrate. Neither autocatalysis nor allostery was included in the reaction mechanism. The features of the reaction were that the oscillations did not occur in a limit cycle and the interval became longer with time. In addition, it was found that the oscillations with an upwardly directed peak occurred at very low concentrations of enzyme in the model of Theorell and Chance. The results were consistent with the experimentally determined data reported previously.

Kinetics of permeation of nucleotide through oil/water interface in the interaction of nucleotide with octadecylamine and dodecyl guanidine

The transports of tritiated ATP, ADP and AMP from the aqueous to scintillator phase with and without octadecylamine (or dodecyl guanidine) have been studied by the layered scintillation method and a theory suitable for an explanation of the results has been presented. (1) Transport processes were all expressed by the first order kinetics. (2) For the simple partitioning of ATP, the reciprocal of the rate constant of the backward permeation was linear with respect to the square of the partition coefficient. (3) For the transport of nucleotide with chemical reaction, the reciprocal of the rate constant of the backward permeation was linear against the overall partition coefficient of nucleotide. (4) A theory was presented on the basis of a general diffusion equation by assuming the two-film model with potential energy near the interface. (5) The theory could explain the dependences of the permeation rates on the partition coefficients. (6) From the finding that the ratio of the apparent diffusion coefficient in aqueous to scintillator phase was much smaller than unity, the occurrence of an energy barrier at interface was suggested. For the simple partitioning of ATP, the energy barrier was not significant.

Oscillatory Reaction of Enzyme Caused by Gradual Entry of Substrate

We have been investigating the oscillatory reaction of enzyme by using semipermeable membrane, by which gradual entry of substrate into enzyme solution is obtained. In the present paper, we investigated oscillatory reaction for enzyme solution wrapped by liposome.