INTERRELATION BETWEEN THE CATALYTIC FUNCTION OF HEME-PROTEINS AND THE STRUCTURAL MODIFICATIONS OF THEIR PROTEIN PARTS

I. SPECTROSCOPICAL OBSERVATIONS MADE ON THE REACTION BETWEEN HEMOGLOBIN AND BENZOATE

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1. Methemoglobin can be converted to a hemichrome like compound through the reaction with benzoate. Absorption figure of this hemichrome derivative is similar to that of the related compound obtained by the reaction with salicylate. Essentially they are similar to that of pyridine hemichrome.
2. Reduced hemoglobin was converted into a hemochrome like FIG. 10. The absorption change of hemichrome on heating.
I. Methemoglobin + benzoate (0.9M).
II. On heating at 90°, this is reversible on cooling.
compound by benzoate. The latter compound gave absorption spectra similar to those of alkali denatured globin hemochrome and of pyridine hemochrome.
3. The relation between the percentage of hemichrome resp. hemochrome formation and the benzoate concentration could be expressed by a sigmoid curve of high order reaction.
4. Much higher concentration of bezoate was needed for the conversion of reduced hemoglobin than for that of methemoglobin. In the concentration of benzoate below 1.0M, the hemichrome formed could be quantitatively converted into reduced hemoglobin through reduction by Na₂S₂O₄. The conversion proceeded through a hemochrome like substance as an intermediary compound which could be observed only transitorily.
5. Glycerol exerted inhibitory effect upon the reaction of hemichrome formation by benzoate.
6. The hemochrome like substance formed by benzoate could not be precipitated on heating. This hemichrome like compound showed a reversible spectral displacement on heating.
I should like to express my thanks to Prof. K, Kaziro and Dr. G. Kikuchi for their interest and helpful discussion during the course of this work.