432 Discussion 



Kamen, M. D. (1957). Research in Photosynthesis. Gatlinburg (Tenn.) Conference, pp. 



149-63. Interscience Publ. Inc., New York. 

 Kamen, M. D. &. Vernon, L. P. (1955). Biochim. biophys. Acta 17, 10. 

 Kamen, M. D. & Vernon, L. P. (1954). J. biol. Cheni. 211, 663. 

 Morton, R. K. (1958). Rev. pure appl. Chem. 8, 161. 

 Newton, J. W. & Kamen, M. D. (1956). Biochim. biophys. Acta 21, 71. 

 Olson, J. M. & Chance, B. (1958). Biochim. biophys. Acta 28, 227. 

 Paul, K. G. (1957). Acta chem. Scand. 5, 389. 

 Sandell, E. S. (1944). Colorimetric Determinations of Trace Metals, Interscience Publ. 



Inc., New York. 

 Smith, L. (1954). Bacterial. Rev. 18, 106. 



Smith, L. & Ramirez, J. (1959). Arch. Biochem. Biophys. 79, 233. 

 Strittmatter, p. & Velick, S. F. (1956). /. biol Chem. 221, 277. 

 Taniguchi, S., Asano, A., Iida, K., Kono, M., Ohmachi , K. & Egami, F. (19 58). Proc. 



int. Symposium Enzyme Chemistry, p. 230. Maruzen Press, Tokyo and Kyoto (1957). 

 Vallee, B. L. (1955). Advanc. Protein Chem. 10, 317. 

 Van Niel, C. B. (1944). Bacterial. Rev. 8, 1. 

 Velick, S. F. & Strittmatter, P. (1956). J. biol. Chem. 221, 265. 

 Vernon, L. P. & Kamen, M. D. (1954). /. biol. Chem. 211, 643. 



DISCUSSION 



The Functions of Cytochrome b^^ and of Cytochroitic c544 

 (Halotolerant Coccus) 



Egami: I would like to summarize the results on cytochrome b^ and on a CO-binding, 

 autoxidizable pigment of a halotolerant bacterium, which Kamen considered to be 

 similar to his RHP. 



Both cytochromes were discovered in my laboratory (in Nagoya) in a halotolerant 

 micrococcus. Halotolerant and halophilic bacteria, which we like to use for the ex- 

 traction of bacterial enzymes, have an advantage in that they lyse easily in distilled 

 water or in dilute salt solution. Thus we can easily extract various bacterial enzymes. 

 Cytochrome b^ was extracted thus in 1953. CO-binding autoxidizable cytochrome 

 c544 (halotolerant micrococcus) was also extracted in the same way later. 



Cytochrome b^ transfers electrons to nitrite and hydroxylamine through nitrite 

 reductase and hydroxylamine reductase respectively. Cytochrome b^ itself is halophilic, 

 e.g. it functions as an electron-transferring enzyme only in relatively concentrated salt 

 solution. Hori and Taniguchi purified 'cytochrome hi by DEAE-cellulose chroma- 

 tography and it was shown that 'cytochrome 64' consisted of a c-type cytochrome (main 

 component), and a b-type cytochrome. Even after purification, the former has a 

 double-peak a-band. 



CO-binding, autoxidizable cytochrome c544, although not yet obtained in homo- 

 geneous state, is presuinably identical with hydroxylamine reductase. Hydroxylamine 

 reductase activity is enhanced by Mn++. According to Taniguchi, the saturation 

 concentration of NH2OH for the enzyme increased with increasing concentration of 

 Mn"" +. It is suggested that Mn++, binding NH2OH and the enzyme (cytochrome (544), 

 participates in the electron transfer between the two substances. 



Nomenclature of CO-binding Pigments 



Morton : The names 'RHP', cytochrome o and cytochrome d call for some comment. 

 In a recent review on cytochromes (Morton, Rev. pure appl. Chem. 8, 161, 1958), 

 I attempted to gather together existing information on properties of cytochromes. 

 As pointed out at that time, I did not wish to propose a new nomenclature but adopted 

 the names in common usage. Only in the case of the 'CO-binding pigments' did I 

 consider it was necessary to point to probable relationships between the pigments of 

 different micro-organisms and I adopted the classification 'cytochrome d' for this 



