Cytochrome c.. 411 



(the heights and positions of the double Sorct peak in acid solutions are not 

 influenced by further acidification): 



Neutral pH: 404 m/^, 551 m^, 594-5 m// 

 AcidpH: 385 m//, 404 m//, 575 m/i, 613-5 m// 



The function of desulphoviridin is unknown. It is associated with various 

 enzymically active fractions of the bacteria but is identical with none. 



METABOLIC FUNCTION OF CYTOCHROME C3 

 Japanese work on this question was summarized by Ishimoto, Kondo, 

 Kamayama, Yagi and Shiraki (1958) and a brief but wider review was given 

 by Postgate (1959). A summary of the present position is given below. 



Thiosulphate or Tetrathionatc Reduction 



Intracellular cytochrome c^ becomes partly oxidized when bacteria are 

 incubated anaerobically with these substrates. Soluble reductase preparations 

 which reduce these substrates in hydrogen have been prepared from the 

 bacteria; the reactions are accelerated by purified cytochrome Cg. Benzyl 

 or methylviologen will act as an artificial electron carrier in place of cyto- 

 chrome C3. 



Dismutation of Formate or Pyruvate 



Cytochrome c.^ accelerates the action of enzyme preparations which 

 dismute formate to hydrogen and COg, but it has no influence on the dis- 

 mutation of pyruvate to acetate, CO2 and H2 (reaction 4). 



Reduction of Colloidal Sulphur, Nitrite, Hydroxylamine, Oxygen 



All these substrates are reduced in hydrogen by cell suspensions or enzyme 

 preparations. With enzyme preparations the reactions are accelerated by 

 cytochrome (3. These reductions, are, however, biochemical artefacts in the 

 sense that they result from direct chemical oxidation of ferro-cytochrome c^ 

 by the substrate and no specific reductase is involved. They can be represented 

 schematically as : 



enzyme (hydrogenase) spontaneous ^,,^ ^^^ 



Ho ^r > cyt . c^ < > NH2OH 



DyestulTs such as benzyl- or methylviologen will replace cytochrome c^ 

 in such reactions. Reactions of this kind may be expected to occur in any 

 system involving low-potential electron transport enzymes; the possibly 

 'artificial' character of certain accepted steps in the reduction of nitrate was 

 pointed out by Senez and Pichinoty (1958). 



