The Amino Acid Requirements of Man

Rose WC, Wixom R. The amino acid requirements of man XTV. The sparing effect of tyrosine on the phenylalanine requirement. J Biol Chem. 1955 217 95-102. 

Rose, W.C., and Wixom, R.L., 1955, The amino acid requirements of man. XIII. The sparing effect of cystine of the methionine requirement, J. Biol. Chem., 216 763-773. 

WC Rose. The amino acid requirements of adult man. Nutr Abstr Rev 27 631-647, 1957. 

The estimation of the individual amino acid requirements of man constitutes a recently opened field of biochemical inquiry. Its advance... 

The proteins of milk are of very high quality, having a biological value of 85 as compared to 50 to 65 for the cereal proteins. They contain, in varying amounts, all of the amino acids required by man. Exceptfor the sulfur-containing amino acids (methionine and cystine), 1 pt (470 ml) of milk supplies the recommended daily allowance of all the essential amino acids. Additionally, the protein to calorie ratio is very favorable in milk, assuring that the consumer is not ingesting empty calories. 

Amino Acid Requirements of Several Invertebrates as Compared to the Rat and to Man... 

Elwyn, D.H., New concepts in nitrogen balance. Can J Gastroenterol, 4, 9A, 1990. Young, V.R., Bier, D.M., and Pellett, P.L., A theoretical basis for increasing current estimates of the amino acid requirements in adult man, with experimental support. Am J Clin Nutr, 50, 80, 1989. 

Organisms such as the red bread mould are able to manufacture not only all of the vitamins, but also all of the amino acids. At some time in our evolutionary history we suffered mutations that resulted in the loss of our power to manufacture the various enzymes involved in these syntheses. Each of these mutations produced in our predecessors a disease-one disease for each vitamin that we now require, and one disease for each of the nine amino acids that are essential for man. Most of us keep these diseases under control by ingesting the proper food. 

The Protein Requirements of Man.—The normal requirement for the human subject is rated at 1 gm. protein per kg. body weight, per diem. This allowance is made on the assumption that the protein of the diet is mixed and of a good quality. The protein intake must provide a sufficiency of the essential amino acids, of which at least five species are necessary tyrosine or phenylalanine, tryptophane, cystine or methionine, lysine and threonine. Digestibility must also be taken into account, and it is now customary to assess proteins in terms of their biological value to the consumer. This is computed by a balance sheet method (Thomas, 1909 Chick, 1936). 

Methanolysis of standard uronic acids has been studied by Inoue and Miyawaki in regard to the depolymerization of chondroitin sulfate and dermatan sulfate. These workers found the glucosiduronic linkage to ga-lactosamine to be rather resistant to methanolysis, but that it is more efficiently cleaved after deamination of the amino galactoside, with its conversion into 2,5-anhydrotalose. For iduronic, glucuronic, and man-nuronic acids released from a polymer, it was found that the peaks monitored for these acids, relative to an internal standard, increase during the first 8 h of methanolysis (M hydrogen chloride, 100°) and remain constant for up to 20 h of methanolysis. This indicated that 8 h is required for complete methanolysis, and that the monosaccharides liberated are stable to the conditions of methanolysis. 

The suggested relationship between numbers ol differences and evolutionary lime is not wholly secure. It assumes uniformity in the tale of clleeiive amino acid substitution, but this rale mas he neither iindorm with time, nor uniform in different pails of the polv vpticle chain. Differences in the rate of effective substitution along Ihe polypeptide chain may be due not only 10 restrictions imposed by the required tertiary structure, hut also to differences in the rate at which various parts of tile l).NA or the gene mutate. The evolution of hemoglobin mav he contrasted w ith that of cytochrome e in which approximately 500 of the molecule appears io have remained invariant purine the lime yeast arid man have evolved. 

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