The cryptoporphyrin of heart muscle

Abstract

Cryptoporphyrin a has been isolated from ox-heart muscle in a yield of about 2–3 mg/kg fresh muscle, and has been obtained as crystalline methyl ester. It has been shown that it is closely related to chlorocruoroporphyrin, but differs from it by a greater molecular weight (700–740 as against 562) and other properties. The increment of the molecular weight is probably present as a large saturated alkyl side chain (R = C 12H 25 — C 15H 31) which has no influence on the spectrum, similar to that found by Warburg and Gewitz 13 in haemin a. Cryptoporphyrin a is, however, spectroscopically quite dissimilar from porphyrin a and closely resembles chlorocruoroporphyrin. Like this, it contains one formyl group and one unsaturated side chain with its double bond in conjugation with the porphyrin ring, in the same relative position on proximal pyrrole rings. The unsaturated group of chlorocruoroporphyrin is vinyl, that of cryptoporphyrin a vinyl or —CH = CHR. Cryptoporphyrin a is not formed from protohaem compounds during the isolation, nor has any evidence been found for it being formed from haemin a. It is therefore unlikely to be derived from cytochrome oxidase or cytochrome a, both of which yield porphyrin a and may well be derived from a so far unknown haemoprotein in heart muscle which has cryptohaem a as its prosthetic group.