Composition of Cytochrome c Oxidase 301 



DISCUSSION 



Function of Copper in Cytochrome Oxidase Preparations 



Slater: I was struck by the fact that in Wainio's Table 1 the copper-haem ratio decreased 

 from 1-9 to 1-2, as the haem-protein ratio increased from 1-2 to 7-0. Does this not 

 suggest that the copper concentration is decreasing as the cytochrome c oxidase is 

 further purified ? 



Wainio: There is only one high value for the copper-haem ratio and that is the first value 

 of 1-9. The others range from 1-2 to 1-4 and are in no particular order. 



Slater: Is it possible that reactivation by copper after diethyldithiocarbamate treatment 

 is due to removal of inhibitory diethyldithiocarbamate by added copper. 



Wainio: This kind of reactivation would be possible only if the reintroduced copper were 

 bound in a loose fashion, because diethyldithiocarbamate will not inhibit the intact 

 enzyme even after one hour of contact. 



Lemberg : We have attempted the addition of copper to various haemoproteins a in the 

 presence or absence of CO, phospholipid, and/or deoxycholate. We have failed to 

 notice any spectroscopic shift by the copper addition which would make the spectra 

 of haemoproteins a more similar to those of cytochrome a and particularly cytochrome 

 Og. We may not have found, of course, the right conditions to reconstitute such a 

 specific copper-haemoprotein as Wainio postulates. 



Falk: There is a certain amount of evidence that copper is required for cytochrome 

 oxidase synthesis in animal tissues, and it is clear also that this enzyme acts in some 

 kind of lipoprotein complex form. I think it is most important, since some people 

 are trying to postulate chemical reaction mechanisms, to try to determine whether 

 the copper is involved mechanistically in the oxidative activity, or is merely necessary 

 for this activity in a secondary way, perhaps such as holding together the haem- 

 protein-lipid complex. An experiment which might throw further light on this might 

 be to try the effect of a bidentate chelator, which might be able to bind the copper 

 but could not co-ordinate with a haem iron. 



