Salmines peptides

Although clupeine and salmine are known to be resistant to the action of pepsin, they are readily hydrolyzed by pancreatic enzymes. Waldschmidt-Leitz et al. [1929 (1), 1931, 1933, 1935 (1)] proposed the following structure for clupeine based on their finding of peptides of the types M A, A M, (A-M A)2, A-Pro-A, and A A in the hydrolyzates of clupeine with various pancreatic enzymes. The structure is of the same type as proposed by Kossel]... 

French biochemists identified many peptides qualitatively on paper chromatograms of the partial hydrolyzates of salmine (described only as of the genus Oncor-hynchus), as also shown in Table VI-2 [Monier and Jutisz, 1954 (1,2)]. From their results, a general structure was suggested for salmine. This formula, in contrast to those described above, is composed of unique sequences of the form M-Arg j, in addition to those of M2 Arg . 

Chart VIII-9. The amino acid sequences of salmine AI, iridine I (a) and (b), and iridine II with demonstration of peptides obtained by enzymic hydrolyses. The symbols used are A, Arg T, tryptic peptide Tm, thermolysin peptide NP, Neutral Protease peptide NP-7-NP, redigested Neutral Protease peptide from NP-No. 7 Tm-6-NP, Neutral Protease peptide from Tm-No. 6 (from Ando and Watanabe, 1969)... 

Table VIII-6. Peptides obtained by Neutral Protease digestion Salmine AI...

The chemical structures of these peptides were established in the usual way by quantitative amino-acid analysis and sequence analysis by a combination of chemical and enzymic methods, including dinitrophenylation, dansylation, Edman degradation, hydrazinolysis and digestion with leucine aminopeptidase and carboxypeptidases A and B. The Neutral Protease peptides of the salmine and iridine components or derivatives thus identified are listed in Table VIII-6 with their recovery values. Differences in the amino-acid sequences and amounts of the peptides obtained from iridine I aroused the suspicion that two molecular species (a and b) were present in the iridine I component. This result, as already described, was supported by observations on the thermolysin peptides of iridine I. 

To summarize for one component of salmine (S-AI) and three components of iridine (I-Ia, I-Ib and I-II) complete amino-acid sequences were deduced as shown in Chart VIII-9, from the information obtained from three sets of peptides resulting from digestion with trypsin, thermolysin, and Neutral Protease, as well as from the N- and C-terminal sequences. 

When clupeine or salmine is treated with concentrated sulfuric acid, N —> O acyl rearrangement takes place at the N-terminal peptide bonds involving serine and threonine residues in a yield of about 70% (Iwai, 1959). In order to achieve selective... 

Monier, R., Jutisz, M. (1) Contribution a Tetude de la structure de la salmine d Oncorhyn-chus. I. Enchainement des aminoacides au voisinage du residu N-terminal et etude de quelques peptides resultant de Thydrolyse acide partiellie. Biochim. biophys. Acta (Amst.) 14, 551—558 (1954). 

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