The Structure of Porphyrin a, Cryptoporphyrin a and Chlorin 82 353 



suggested. In spite of its larger molecular weight, cryptohaemin remains 

 together with protohaemin in the aqueous phase of the Rawlinson distribution 

 between ether-pyridine and aqueous pyridine-HCl (Rawlinson and Hale, 

 1949), and also in the aqueous phase in the countercurrent distribution phase 

 between light petroleum-acetone and aqueous HCl-acetone of Kiese and 

 Kurz (1954), thus differing from porphyrin a of similar molecular weight. 



Cryptoporphyrin a is not an artifact derived from protohaem. Removal 

 of myoglobin from heart muscle before processing greatly decreases the 

 protoporphyrin yield, but does not decrease the cryptoporphyrin yield. 

 Porphyrins of similar spectroscopic properties can be obtained from red 

 cells (cryptoporphyrins/?) but these are chemically quite different compounds; 

 they contain a ketonyl side chain and chlorine, not a formyl side chain (Lem- 

 berg, 1953; Clezy and Parker, unpubhshed). 



At first it was assumed (Lemberg, 1953; Lemberg and Parker, 1955) that 

 cryptoporphyrin a was an artifact derived from porphyrin a by alteration 

 during the isolation process. Its yield, though always much smaller than that 

 of porphyrin a varied considerably, and porphyrin a gave rise to a porphyrin 

 resembling cryptoporphyrin a during treatment with acetone-HCl and 

 reintroduction and removal of iron. It could be shown, however (Parker, 

 1959), that the altered porphyrin a thus formed was not identical with 

 cryptoporphyrin a, while its formation in variable amounts can explain the 

 apparent variation in yield. The variation was also less in later experiments. 

 The yield of cryptoporphyrin a from heart muscle is between 5% and 10% 

 that of porphyrin a. 



These results make it likely that cryptoporphyrin a is derived from a so 

 far unknown haemoprotein of heart muscle which has cryptohaem a as its 

 prosthetic group. Connelly, Morrison and Stotz (1958) have independently 

 come to the same conclusion by chromatographic separation of heart muscle 

 haemins on silica gel. A reservation must be made, however. The spectrum 

 of the porphyrin obtained from their "haemin a^' (Morrison, Connelly and 

 Stotz, 1958) is not identical with that of cryptoporphyrin a, since its spectrum 

 in ether is compared with that given by Lemberg (1953) for a solution of 

 cryptoporphyrin a in chloroform. We have also found cryptoporphyrin a 

 in chicken heart and liver. 



Pyridine cryptohaemochrome a differs from pyridine haemochrome a 

 in the position of its a-band by 6 m//, and in having a second absorption band 

 in the green. Owing to these relatively small differences and the low concen- 

 tration of cryptohaem a, it will be very difficult to discover the cryptohaemo- 

 protein a in cytochrome oxidase preparations or in tissues. Its low concentra- 

 tion would not appear to suggest for it a role in the main respiratory chain, 

 nor can it be the prosthetic group of cytochrome a or ^3. However, its dis- 

 covery shows that careful chemical isolation can still give results unobtainable 

 by spectroscopic methods alone. 



