Radiation-Induced Enhancement of Nitrite Reducing Activity of Cytochrome c

• Published in: Journal of agricultural and food chemistry 2003-11, Vol.51 (23), p.6835-6843
• Main Authors: Suruga, Kohei, Nagasawa, Naotsugu, Yamada, Seiji, Satoh, Tadashi, Kawachi, Ryu, Nishio, Toshiyuki, Kume, Tamikazu, Oku, Tadatake
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Circular Dichroism; Cytochromes c - chemistry; Cytochromes c - radiation effects; Drug Stability; Food industries; Fundamental and applied biological sciences. Psychology; Gamma Rays; General aspects; Heme - chemistry; Hygiene and safety; Methionine - chemistry; Nitrite Reductases - metabolism; Nitrites - chemistry; Oxidation-Reduction; Protein Folding
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0345651

Commercial cytochrome c (Cyt c) was irradiated with Co-60 γ-rays in the dose range of up to 3.0 kGy to investigate the enhancement of the nitrite reducing activity of Cyt c. The optimum irradiation dose to induce nitrite reducing activity for 30 μM Cyt c solution was 1.0 kGy under an O2 atmosphere. The nitrite reducing activity of Cyt c irradiated at this dose was approximately 45-fold that of unirradiated Cyt c and ca. 1.2-fold that of nitrite reductase. The irradiation treatment resulted in unfolding of the peptide chain, exposure of the heme group, oxidation of methionine to methionine sulfoxide, dissociation of the sixth ligand (Met), and occurrence of autoxidation in Cyt c. Sepharose-immobilized irradiated Cyt c had a similar activity to that in solution. The resin retained the activity after five uses even after 1 year of storage. The irradiated Cyt c will be able to be used as a substitute for nitrite reductase. Keywords: Cytochrome c; γ-irradiation; nitrite reducing activity