Bjarnason-Baumann/Pfaender /Sieben
170 (414)
Second European Nutrition Conference, Munich 1976 Nutr. Metab. 2 / (Suppl. 1): 170-171 (1977)
Enhancement of the Biological Value of Whey Protein by Covalent Addition into Peptide Linkage of Limiting Essential Amino Acids Barbara Bjarnason-Baumann, Peter Pfaender and Gunther Sieben Institute of Biological Chemistry, University of Hohenheim, Hohenheim
Downloaded by: University Toronto Libr. 142.150.190.39 - 1/7/2020 4:26:14 PM
In many parts of the world relatively large amounts of protein are available, though usually of rather low biological value. If supplemented with limiting essential amino acids, optimal utilization is observed when such additions are present in peptide linkage. We have therefore investigated whether the substitu tion of a protein by N-carboxyanhydrides of limiting amino acids under mild simple reaction conditions (1) would lead to an improvement of its biological value. The test material constitutes whey protein concentrate. The FAO Provi sional Reference Protein was taken as reference for the determination of the limiting amino acids. In whey protein tyrosine (108.9 mg AA/g N), methionine (95.8 mg AA/g N), phenylalanine (94.6 mg AA/g N) and isoleucine (71.1 mg/ AA/G N) are limiting in that order with the amounts given in parentheses as the differences to the ‘FAO’ amino acids composition. The deficiency in Phe + Tyr was counterbalanced by Phe because of the well-known metabolic route of Phe -»Tyr. Two preparations have been made, one with whey protein plus L-Phe to cover the deficit in Tyr and Phe, and another to cover the deficit in all four amino acids, the latter containing 112 % Phe plus Tyr, 115 % Met and 101 % lie, respectively, when related to the FAO Reference Protein. The samples were analyzed according to Hegsted et al. (2) for the estimation of the relative nutri tive value of protein by the slope ratio assay with young rats. Three levels of proteins (N X 6.25), 3.0, 5.4 and 7.7 % of untreated whey, single and triple substituted whey, respectively, and whole egg protein as standard were fed to weanling rats. The values of relative nutritive value were almost identical when obtained from body water, body nitrogen or weight gain; 0.75 for whey protein, 0.89 for Phe-substituted whey protein, and 0.92 for multiple substitution of whey protein were found. Covalent introduction of limiting amino acids into protein has therefore led to a highly significant enhancement of the biological value of feed proteins. Such covalent introduction of amino acids seems to be applicable to every type of protein.
Protein Improvement
171 (415)
References 1 2
Pfaender, P.; Pratzel, H., and Blecher, H.: Process and apparatus for the synthesis of peptides by use of N-carboxyanhydrides. US Patent 3,951,741 (1976). Hegsted, D.M.; Neff, R., and Worcester, J.: Determination of the relative nutritive value of proteins. Factors affecting precision and validity. J. agric. Fd Chem. 16: 190-195 (1968).
Prof. Dr. G. Siebert, Institute of Biological Chemistry, University of Hohenheim, D -7000 Stuttgart (FRG)
Second European Nutrition Conference, Munich 1976 Nutr. Metab. 21 (Suppl. 1): 171-172(1977)
Nitrogen Utilization of Proteins and Their Corresponding Aniino Acid Mixtures Studied in Growing Rats Elisabeth Forsum and L eif Hambraeus Institute of Nutrition, University of Uppsala, Uppsala
It is well known that protein requirements can be met by mixtures of synthetic amino acids. Recently, however, it has become evident that dietary protein is absorbed not only as free amino acids but also as small peptides. Furthermore, the rate of absorption for a mixture of peptides is higher than that for a mixture of free amino acids. Earlier studies (2) have indicated that the amino acids of intact proteins are utilized more efficiently for protein synthesis than mixtures of free amino acids simulating these proteins. However, there also are several reports in the literature which found no differences between intact protein and free amino acid mixtures. It is of interest to study this question further since amino acid mixtures frequently are used in clinical nutrition. In the study to be reported four proteins (casein, gluten, soy and egg albu min) were compared to their corresponding amino acid mixtures.
Methods
Downloaded by: University Toronto Libr. 142.150.190.39 - 1/7/2020 4:26:14 PM
Amino acid composition of the native proteins was estimated as described by For sum (3). Experiment I. Test diets were given to weaning male rats, 21 days of age, for estima tion of nitrogen efficiency ratio (NER) (1). At the start of the experiment five rats were
170 (414)
Second European Nutrition Conference, Munich 1976 Nutr. Metab. 2 / (Suppl. 1): 170-171 (1977)
Enhancement of the Biological Value of Whey Protein by Covalent Addition into Peptide Linkage of Limiting Essential Amino Acids Barbara Bjarnason-Baumann, Peter Pfaender and Gunther Sieben Institute of Biological Chemistry, University of Hohenheim, Hohenheim
Downloaded by: University Toronto Libr. 142.150.190.39 - 1/7/2020 4:26:14 PM
In many parts of the world relatively large amounts of protein are available, though usually of rather low biological value. If supplemented with limiting essential amino acids, optimal utilization is observed when such additions are present in peptide linkage. We have therefore investigated whether the substitu tion of a protein by N-carboxyanhydrides of limiting amino acids under mild simple reaction conditions (1) would lead to an improvement of its biological value. The test material constitutes whey protein concentrate. The FAO Provi sional Reference Protein was taken as reference for the determination of the limiting amino acids. In whey protein tyrosine (108.9 mg AA/g N), methionine (95.8 mg AA/g N), phenylalanine (94.6 mg AA/g N) and isoleucine (71.1 mg/ AA/G N) are limiting in that order with the amounts given in parentheses as the differences to the ‘FAO’ amino acids composition. The deficiency in Phe + Tyr was counterbalanced by Phe because of the well-known metabolic route of Phe -»Tyr. Two preparations have been made, one with whey protein plus L-Phe to cover the deficit in Tyr and Phe, and another to cover the deficit in all four amino acids, the latter containing 112 % Phe plus Tyr, 115 % Met and 101 % lie, respectively, when related to the FAO Reference Protein. The samples were analyzed according to Hegsted et al. (2) for the estimation of the relative nutri tive value of protein by the slope ratio assay with young rats. Three levels of proteins (N X 6.25), 3.0, 5.4 and 7.7 % of untreated whey, single and triple substituted whey, respectively, and whole egg protein as standard were fed to weanling rats. The values of relative nutritive value were almost identical when obtained from body water, body nitrogen or weight gain; 0.75 for whey protein, 0.89 for Phe-substituted whey protein, and 0.92 for multiple substitution of whey protein were found. Covalent introduction of limiting amino acids into protein has therefore led to a highly significant enhancement of the biological value of feed proteins. Such covalent introduction of amino acids seems to be applicable to every type of protein.
Protein Improvement
171 (415)
References 1 2
Pfaender, P.; Pratzel, H., and Blecher, H.: Process and apparatus for the synthesis of peptides by use of N-carboxyanhydrides. US Patent 3,951,741 (1976). Hegsted, D.M.; Neff, R., and Worcester, J.: Determination of the relative nutritive value of proteins. Factors affecting precision and validity. J. agric. Fd Chem. 16: 190-195 (1968).
Prof. Dr. G. Siebert, Institute of Biological Chemistry, University of Hohenheim, D -7000 Stuttgart (FRG)
Second European Nutrition Conference, Munich 1976 Nutr. Metab. 21 (Suppl. 1): 171-172(1977)
Nitrogen Utilization of Proteins and Their Corresponding Aniino Acid Mixtures Studied in Growing Rats Elisabeth Forsum and L eif Hambraeus Institute of Nutrition, University of Uppsala, Uppsala
It is well known that protein requirements can be met by mixtures of synthetic amino acids. Recently, however, it has become evident that dietary protein is absorbed not only as free amino acids but also as small peptides. Furthermore, the rate of absorption for a mixture of peptides is higher than that for a mixture of free amino acids. Earlier studies (2) have indicated that the amino acids of intact proteins are utilized more efficiently for protein synthesis than mixtures of free amino acids simulating these proteins. However, there also are several reports in the literature which found no differences between intact protein and free amino acid mixtures. It is of interest to study this question further since amino acid mixtures frequently are used in clinical nutrition. In the study to be reported four proteins (casein, gluten, soy and egg albu min) were compared to their corresponding amino acid mixtures.
Methods
Downloaded by: University Toronto Libr. 142.150.190.39 - 1/7/2020 4:26:14 PM
Amino acid composition of the native proteins was estimated as described by For sum (3). Experiment I. Test diets were given to weaning male rats, 21 days of age, for estima tion of nitrogen efficiency ratio (NER) (1). At the start of the experiment five rats were
