334 



Discussion 



identify the non-purified "cryptoporphyrin" of Lemberg and Falk with the pure, 

 crystalline cryptoporphyrin a as isolated by Parker. 



Mitochrome in Relation to Cryptohaem a 



Morell: The preparation of cytochrome oxidase which Morrison has aged to obtain 

 the cryptohaem a-like compound is similar to those reported to give 'mitochrome'. 

 According to Elliott, Hiilsmann and Slater {Biochim. biophys. Acta 33, 509, 1959), 

 'mitochrome' from cytochrome oxidase preparations contains a modified haem a 

 which gives a haemochrome band with pyridine at 575 m/i. Our pyridine crypto- 

 haemochrome a has its a band at 581 mix. Thus aged cytochrome oxidase preparations 

 give at least one modified haem a which is not cryptohaem a. 



Slater: The difference between the pyridine haemochrome isolated from mitochrome 

 obtained by ageing of cytochrome a + 03, and that obtained by Morrison from his 

 aged preparation is paralleled by a difference in the position of the y-bands of the 

 two preparations. 



It appears, then, either that the transformation of cytochrome (a + 03) has not 

 proceeded all the way to mitochrome in Morrison's aged preparation, or that the 

 latter is a mixture of cytochrome a -\- a^ and mitochrome, yielding a mixture of the 

 two pyridine haemochromes. 

 Morrison: There are two things that are disturbing about the results that Slater cites. 

 The first is the fact that one can obtain mitochrome whether one starts with a cyto- 

 chrome b preparation or a cytochrome c oxidase preparation. These preparations are 

 quite different in both enzymic properties and the nature of their haem groups. 



The second is that the mitochromes derived from cytochrome b or cytochrome c 

 oxidase appear to be identical spectrally. Yet the haemins derived from the respective 

 mitochrome preparations are quite different, having pyridine haemochromes whose 

 a peaks are 1 7 m/t apart. 



It is interesting that a haemochrome with an a peak at 575 m/< has been described 

 by Lemberg and termed cryptohaemochrome p. This compound was derived from 

 oxidative procedures applied to protohaemin. Slater's compound, however, appears 

 to have been derived from haemin a or cryptohaemin a. 



Slater's suggestion that our results might be explained by virtue of a mixed haemo- 

 chrome is not valid since we chromatographed our material. 



