Die Aminosäure‐Sequenz vom Cytochrom c des Karpfens, Cyprinus carpio

Cytochrome c was isolated in pure form form hearts of the carp, Cyprinus carpio , by means of ion exchange chromatography and gel filtration. The protein had an iron content of 0.44% and showed an absorption spectrum characteristic of cytochrome c molecules. The ratio of the optical density at 550 nm of the reduced from to that at 280 nm of the oxidized form of the protein was 1.06 to 1.08. The protein was digested with trypsin or with a trypsin preparation which contained some chymotryptic activity. The resulting peptides were resolved on thin layer plates by electrophoresis and chromatography. The amino acid compositions of 40 peptides isolated from the fingerprints were analyzed. The sequences of 22 of these peptides representing the complete polypeptide chain of carp cytochrome c were determined. By comparing the peptides with the sequences of other vertebrate cytochromes c and by using the overlapping compositions of some peptides obtained by tryptic digestion or by splitting the protein with cyanogen bromide the complete sequence of 103 residues was deduced. Two types of cytochrome c have been found in our material differing at residue 4 of their sequences by glutamic acid (iso‐1‐cytochrome c ) or aspartic acid (iso‐2‐cytochrome c ). The origin of these two types is supposed to be a racial heterogeneity of carps used for human nutrition. Carp cytochrome c differs from cytochrome c of tuna in at least 8 residues, and from cytochrome c of the dogfish ( Squalus sucklii ) in at least 12 to 14 residues depending in this case on the location of a residue deleted in the cytochromes c of both bony fishes. Deviating from other vertebrates so far known the three species of fish have in common an asparagine at residue 22 and a serine at residue 54 of their cytochromes c .