Journal of Nutrition

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Journal of Nutrition Vol. 60 No. 1 September 1956, pp. 105-120
Copyright © 1956 by American Society for Nutrition
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The Pepsin-Digest-Residue (PDR) Amino Acid Index of Net Protein Utilization1

A. Leonard Sheffner, Gladys A. Eckfeldt and Harry Spector

Nutrition Branch, Quartermaster Food and Container Institute for the Armed Forces, Chicago, Illinois

The relationship between the pattern of amino acids released by digestive enzymes and the biological value of food proteins was studied. The pattern of amino acids released in vitro by pepsin revealed differences between proteins which were not apparent from their total essential amino acid content nor from the patterns existing when the pepsin digests were further digested with trypsin and erepsin.

An amino acid index is described which takes into account the physiological availability of amino acids during digestion. The new index combines the pattern of essential amino acids released by in vitro pepsin digestion with the amino acid pattern of the remainder of the protein to produce an integrated index — the Pepsin-Digest-Residue (PDR) amino acid index. The PDR index was closely correlated with the net protein utilization value of a variety of proteins. Division of the PDR index by the digestibility coefficient of the respective proteins yielded values which accurately predicted the biological values of the proteins studied.

1 A preliminary report of this work was presented before the American Society of Biological Chemists at San Francisco, California, April 11–15, 1955 (Sheffner, Eckfeldt and Spector, '55).

Manuscript received 26 March 1956.




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