STUDIES ON ENZYMIC NITRITE REDUCTION

I. PROPERTIES OF THE ENZYME SYSTEM INVOLVED IN THE PROCESS OF NITRITE REDUCTION

Abstract

1. Electron transport system functioning in the reduction of nitrite and the properties of NiR were studied using a halotrelant Micrococcus (strain 203) as the material.
2. Ferrocytochrome b, reduced nitrite in the presence of NiR. The reaction required high salt concentrations.
3. Electron transport from DPNH to nitrite, requiring high salt concentrations, was activated by FAD about two-fold, and inhibited by antimycin A.
4. Glucose-NiR system was inhibited by amytal, quinine, dicumarol and antimycin A, and activated by FAD and menadione.
5. Succinate-NiR system was inhibited by antimycin A but not inhibited by amytal, quinine and dicumarol.
6. NiR was inhibited by cyanide, azide and metal chclators. The carbon monoxide inhibition in the dark was not reversed by light. Hydro-xylamine inhibited the MbH₂-NiR system but did not inhibit the PMSH-NiR system. The nitric oxide inhibition at 0.1 atm. was stonger in MbH₂-NiR system than in PMSH-NiR system.
7. The similarity of the electron transport system investigated to the mammalian terminal oxidase system was discussed.
8. The electron transport system functioning in the reduction of nitrite may by summarized as shown in Fig. 4
. The author wishes to thank Prof. F Egami for his kind encouragement and guidance, and Dr. S. Taniguchi, Mr. K. Ohmachi and Mr. E. Itagaki for their helpful discussion. He also wishes to express his thanks to Prof. T. Mori and Dr. H. Iwasaki of the Department of Biology, Nagoya University for their helpful suggestion.