The Quality of Proteins

Abstract

It is the amino-acid composition of the proteins in relation to the needs of the organism at the moment which is our main concern, but before I pass to the main topic of our discussion I would remind you that it is the physico-chemical character of the proteins of wheat 0 0~ which governs the texture of bread, the caseinogen of milk, its curd, and the coaguhtive properties of native proteins, the vast array of appetizing egg dishes. Historim1The pioneer experiments of Willcock and Hopkins (1906-07) and of Osborne and Mendel (1914) on the effect on growth of proteins lacking certain amino-acids were subsequently brought to a new stage when Rose, one of Mendel's most distinguished pupils, determined the amino-aoids indispensable for the growth of the rat. Rose defined an indispensable dietary component as "one which cannot be synthesized by the animal organism, out of the materials ordinarily available at a speed commensurate with the demands for normal growth". Almquist, Jackson, Albanese, Holt, Mitchell and their collaborators have added to this knowledge by studies on animals, including man. As Dr. C. P. Stewart will be dealing in detail with this aspect (Stewart, 1946), I will simply mention that of the amino-acids which Rose (1938) and Rose and Rice (1939) found essential for the normal growth of the rat and dog, namely, valine, methionine, histidine, lysine, tryptophane, phenylalanine, threonine, leucine, isoleucine and arginine, Rose, Johnson (1942), Rose, Haines, Johnson and Warner (1943) and Albanese, Holt, Frankston, Kajdi, Brumback and Wangerin (1943) have already demonstrated that for men all these, with the exception of histidine, appear to be essential for full functional maintenance. The transamination shuttle mechanism described by Braunstein and Kritzman (1937), and the transmethylation mechanism revealed by D u Vigneaud, Chandler, Cohn and Brown (1940) VOL. 4, 19461 217 BUCKSBURN, ABERDEEN, OCTOBER 20TR, 1945 Nutr. Abstr. Rev. 4,447. Personal communication. Ann, Circ. Ill. agric. Exp. Sta. no. 369. Lancet, 242, 405. Bwchem. J . 39, xxii. Lancet, 248, 266. Nutr. Abstr. Rev. 10, 1. Brit. med. BuU. 2, 207. Brit. med. BUZZ. 3, 96. J . biol. J. A m r . diet. Ass. 20, 81.