Protein evaluation based on intermediary protein metabolism criteria

Abstract

The activities of ornithine carbamyl transferase, arginase and glutamic-pyruvic transaminase increase in the liver of the rat if the biological value of the dietary protein decreases. Experiments with pigs revealed in the blood serum an analogous high correlation between the biological value of the dietary protein and the activities of arginase, glutamic-pyruvic transaminase, leucine aminopeptidase and glutamic-oxalacetic transaminase. The most favourable possibility of protein evaluation on the basis of criteria of the intermediary protein metabolism consists in the determination of the blood urea concentration provided that the protein carrier supply is standardized. This procedure which has been elaborated by BERGNER and co-workers in 1968 for the determination of the protein quality was confirmed by TAYLOR and co-workers in 1974 on healthy individuals as a reliable and elegant measuring technique with highly significant correlation. It is concluded that the true biological value of protein carriers or protein mixtures which are intended for human nutrition can on principle be determined only in studies with healthy individuals.