Abstract
Thiaminase II, a hydrolytic enzyme, catalyzes the reaction between thiamine and water. On the other hand, it can also be presumed that the reaction between thiamine and OH ion may be an essential one. In either case of these two types, the reaction belongs to a second order reaction. Thus the general enzyme-kinetics in the second order enzymatic reaction were studied under the condition that one of two substrates was kept at a constant concentration throughout the reaction. New equations of the second order enzymatic reaction were presented. From these equations the following results are expected, when the two substrates are represented as A and B, and when the substrate B is kept at a constant concentration during the reaction : In the case of high concentration of B such as H_2O, the type of equation becomes similar to the Briggs-Haldane's type of Michaelis-Menten's equation. In the case of low concentration of B such as OH ion, the equations suggest that the inhibitory effect may be brought about by the substrate A, and that the values corresponding to Km may be changed by the concentration of B. The thiaminase II catalysis showed practically such results as expected from the consequences in the case of low concentration of B. Then the enzymatic reaction should essentially be a second order reaction between thiamine and OH ion.
