Factors Influencing the Biosynthesis of the Tyrosine-rich Proteins of Wool

Abstract

The tyrosine content of wool can vary from about 2·3 to 4·4% of the amino acid residues. This variability, which can be attributed mostly to differences in the proportion of high-tyrosine proteins, appears to be partly of genetic and partly of dietary origin, for there are considerable differences in high-tyrosine protein content between the wools from different breeds of sheep and individual sheep of the same breed, and abomasal infusions of zein, maize gluten and wheat gluten strongly repress the synthesis of these proteins. Infusions of an amino acid mixture simulating the composition of zein produced a similar effect to that of zein. No significant reversal of the repression was produced by adding lysine, tryptophan or tyrosine to zein. It is suggested that these inhibitions may result from interference with aromatic amino acid metabolism.