The Amino Acids in Nutrition.
Year: 1932
Type: article
Abstract: The past thirty years have witnessed a remarkable change in knowledge regarding the importance of the nitrogenous portion of the ration. At the beginning of the twentieth century comparatively little quantitative information was available concerning the chemical make-up of proteins. The majority of the amino acids had been discovered prior to 1900, but very limited data existed concerning their relative distribution. Consequently, there appears to have been little appreciation of the fact that the nutritive value of a protein depends upon the kind and quantities of its components. Under the circumstances, it is not surprising that emphasis should have been placed upon the amount of protein ingested without much reference to possible differences in nutritive quality. The advent of the Kossel and Kutscher34 procedure for the isolation of the diamino acids, and the Fischer20 ester method for the separation of the monoamino acids marked the beginning of a new era in knowledge not only of the chemistry of proteins, but indirectly of their physiological value as well. It was soon seen that proteins of different sources vary enormously as regards the proportions in which their constituent amino acids occur. Frequently, one or more amino acid was found to be missing entirely. Thus gliadin of wheat proved to be deficient in lysine; zein of corn was shown to be practically devoid of lysine and tryptophane; and gelatin was seen to be lacking in tryptophane, tyrosine, cystine, valine, isoleucine, and hydroxyglutamic acid (cf. Dakin14). The recognition of these facts naturally raised the question as to the biochemical importance of the individual amino acids. Inasmuch as all of the generally recognized amino acids occur as components of tissue proteins, obviously each must be made available, either preformed in the diet, or by synthesis in the organism from other materials. Thus protein metabolism immediately became a much more complex phenomenon than was originally supposed. Instead of being concerned with a single dietary factor, it was now seen to involve each of the so-called "Bausteine " of proteins of which eighteen (including norleucine) had been discovered
Source: PubMed Central
Author: W C Rose
Language: English
Subfield: Food Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1850068953