352 R. Lemberg, P. Clezy and J. Barrett 



because most of our porphyrin a preparations still contain lipid impurities 

 in amounts of the same order as the large alkyl side chain. 



The position of these alkyl groups (or group) and their structure is of 

 interest for the problem of the biosynthesis of haem a. The formyl group 

 would not appear to present a problem; it can arise by oxidation of a methyl, 

 as in chlorophyll b, leading to a porphyrin of formula II (Fig. 3); or, leading 

 to a porphyrin of formula I, by oxidation of a vinyl, since in chlorocruorin 

 formyl is found instead of a vinyl in haemoglobin. Formation of an a-hydroxy- 

 ethyl side chain (in position 2) from vinyl also can easily be understood, since 

 Granick, Bogorad and Jaffe (1953) have found this group in porphyrins from 

 Chlorella mutants. The formation of an a-hydroxyalkyl group, other than 

 a-hydroxyethyl, would, however, require a different explanation. The 



• CH : CH • R group can arise either by condensation of • CH3 (or an original 



• CH2CO2H side chain) with a fatty aldehyde, which would explain the double 

 bond joining it to the porphyrin ring; or by one molecule of succinyl co- 

 enzyme A being replaced in the synthesis by the coenzyme A compound of 

 an a,/3-unsaturated fatty acid. 



CRYPTOPORPHYRIN A 



The fractionation with hydrochloric acid of porphyrins from heart muscle 



by the Willstatter procedure yielded in the 8% HCl fraction a porphyrin 



which could not be a mixture of protoporphyrin with 



/h porphyrin a, since the ratio £'580m;</^5i3m/. of the porphyrin 



^(>) in ether was 0-65, identical with that of protoporphyrin 



and different from that of porphyrin a (1*2), whereas a 



\^ X distinct absorption band at 555 n\fi could be observed 



P P (Lemberg, 1953; Lemberg and Parker, 1955). By alumina 



Fig. 4. chromatography and crystallization from ether at low 



Cryptoporphvrin a temperature, the well-crystallized methyl ester, m.p. 259- 



260°C was obtained (Parker, 1959). 



The absorption spectrum of cryptoporphyrin a is very similar to that of 



chlorocruoroporphyrin (Table 1) and R III/IV of the two porphyrins is 



also similar. Cryptoporphyrin a contains one formyl group and one vinyl 



(or alkylvinyl) side chain in the same relative position to one another as in 



chlorocruoroporphyrin. However, the specific extinctions of cryptoporphyrin 



a show that the molecular weight is similar to that of porphyrin a and larger 



than that of chlorocruoroporphyrin, and indicate that cryptoporphyrin a 



contains a large alkyl group. The formula given in Fig. 4 which differs from 



that of chlorocruoroporphyrin only by its R group on the vinyl group has 



been suggested (Parker, 1959). Barrett (unpublished) has found that the 



resorcinol melt yielded a porphyrin of deuteroporphyrin type, but insufficient 



material has been available for exact identification of this porphyrin with 



deuteroporphyrin which would result from a porphyrin of the formula 



