The amino acid composition of mammalian collagen and gelatin

Abstract

The amino acid composition of collagen or gelatin from 5 species of mammals (man, ox, pig, whale and wallaby) was determined by ion exchange chromatography. Results obtained for oxhide gelatin are in good agreement with previously published values, except for alanine and serine. The composition of gelatin is closely similar to that of the collagen preparations, suggesting that gelatin is representative of the main protein constituent of collagenous tissues in amino acid composition. The collagen of the land placentals studied did not show any marked variation between species. The content of serine and threo-nine in whale gelatin exceeded that in land mammals, but was not so high as that from other classes of marine vertebrates. Wallaby collagen also contained very slightly higher amounts of serine and threo-nine than the other land mammals. There were no significant differences in amino acid composition between two gelatins, serially extracted from limed oxhide. These gelatins differed in rigidity properties, although viscosity measurements indicated that they had the same average molecular weight. Gelatin contained less tyrosine than the collagenous precursors. Fractionation of gelatin with ethanol to remove impurities led to a further reduction in tyrosine content. It has not yet been proved that tyrosine is a true constituent of gelatin.