ON THE INTERMEDIATE COMPOUND BUILT IN THE PROCESS OF CATALASE REACTION

抄録

(1) In, continuation of works previously reported, quantitative studies were made on the transition phenomena occuring in the inhibitory action of various poisons upon catalase reaction. Further evidence was adduced in support of the hypothesis, advanced in the preceding paper, that the “fina” state of inhibition is brought about by the reaction of the poison with the catalase-H₂O₂-complex which is formed in an intermediate step of the catalase reaction.
(2) Using azide and o-chlorophenol, the velocity constant of the reaction between the catalase-H₂O₂-complex in question and the -poisons was determined. From the data on the effect of ionic -strength of the medium upon the velocity of the said reaction, it was concluded that the reaction between the complex in question and azide is non-ionic, while the reaction between the complex and, -o-chlorophenol is ionic.
(3) By the pretreatment-technique, as was effected with H₂O₂ in our previous work, it was shown that a compound quite homolo-gous to the catalase-H₂O₂-complex mentioned above is formed bet-ween catalase and monomethyl hydrogen peroxide. This compound was found to combine with various poisons with the affinities which are of the same order of magnitude as those shown by the catalase-H₂O₂-complex towards the respective poisons.
(4) It was discussed that the cat alase-H₂O₂-complex, the formation of which was studied kinetically by Chance using the technique of flow-method, is nothing but the complex postulated in the authors' theory. Taking duly into account the data reported by Chance (8) and by Bonnichsen, Chance and Theorell (9) and also by using some data obtained in the authors' experiment to be reported later, concrete values of velocity constants were assigned to each intermediate step of catalase reaction assumed in the authors' theory. It was thus shown that the kinetic schema:
E+S_??_^SE
^SE+S_??_S^SE
S^SE→E+2H₂O+O₂
(E: free catalase molecule, S: hydrogen peroxide, ^SE: the intermediate complex, S^SE: a complex in which another molecule of H₂O₂ s is bound reversibly to ^SE), represents the simplest and satisfactory picture in alignment with all kinetic evidences known for the process of H₂O₂ decomposition by catalase.
The authors desire, in this opportunity, to thank Dr. H. TAMIYA for his -encouragement and support in carrying out this research. Thanks are also due to the Ministry of Education for a grant which enabled the research to be carried out.