|The amino acid composition of fish muscle proteins|
Hamoir, G. (1962). The amino acid composition of fish muscle proteins, in: Heen, E. et al. Fish in nutrition. pp. 73-75
In: Heen, E.; Kreuzer, R. (1962). Fish in nutrition. Fishing News (Books): London. XXIII, 447 pp., more
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VLIZ: Biological Resources 
Present evidence points to the existence of a fundamental amino-acid plan for the constitution of the proteins of the myofibril: myosin, actin and tropomyosin, of the lower as well as the higher vertebrates. The opposite, however, occurs in the case of the proteins dissolved in the sarcoplasm (myogen). The electrophoretic patterns of the myogens of fish are characteristic of each species; they differ from those of warm-blooded vertebrates by a common higher average mobility. On the other hand, the myogens of fish contain proteins having rates of sedimentation of 1.3-1.5, 4.5-5.0 and 6.5-7.2 S. The first group is absent in the case of warm-blooded vertebrates myogens. It amounts to as much as about 50 per cent in carp myogen. When isolated and subjected to electrophoresis at neutral pH, this fraction resolves in the case of the carp into three peaks. Two components migrating at the levels of the second and third peaks have been isolated. The study of their properties has shown that their molecular weight is around 14,000, and their amino-acid compositions extremely abnormal. A major component, having a rate of sedirnentation of 5 S and a high electrophoretic mobility, has also been isolated from carp myogen. A corresponding component does not seem to exist in warm-blooded vertebrates. lnvestigations carried out on carp aldolase and carp glyceraldehyde deshydrogenase have shown that their electrophoretic mobilities are low at ph 7, and sirnilar to (if not identical with) those of the corresponding rabbit muscle enzymes. These results suggest that, as against the myogen of warm-blooded animals which is usually assumed to be made up mainly of glycolytic enzymes, the myogen of cold-blooded vertebrates contains three distinct groups of proteins: the first one, not observed in the case of other vertebrates and containing proteins of small molecular weight and very unusual amino-acid composition; a second one, with a sedimentation rate of 5 S and a fairly high electrophoretic mobility; and a third one corresponding to glycolytic enzymes. Some components of the fish myogen may form a protein reserve, or may have some biological function not occurring in warm-blooded muscle which has still to be defined.