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Availability of essential amino acids from proteins. II. —food proteins
Author(s) -
Dvořák Z.
Publication year - 1968
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740190204
Subject(s) - leucine , aminopeptidase , papain , biochemistry , amino acid , dipeptidase , trypsin , exopeptidase , hydrolysis , hydrolyzed protein , chemistry , pepsin , enzyme , biology
The availability of leucine from L‐leucinamide hydrochloride, L‐leucyl‐glycyl‐glycine and glycyl‐L‐leucine as substrates for leucine aminopeptidase and glycyl‐leucine dipeptidase was studied with Streptococcus faecalis, S. zymogenes and Lactobacillus arabinosus. The results indicate that these micro‐organisms have their own activity of exopeptidases through which they may utilise amino acids of peptides, released from the proteins by hydrolysis by endopeptidases. The availability of leucine from the proteins of beef muscle, hydrolysed by pepsin, trypsin, pancreatin or papain was also studied. The amount of available leucine found differed according to the enzyme and micro‐organism used. Most efficient were pancreatin and papain. The calculated total amount of leucine present in the proteins studied was not found experimentally by digestion with any of these enzymes. Further hydrolysis by leucine aminopeptidase increased the availability of leucine to 84.6‐100%. By using leucine aminopeptidase simultaneously with prolidase, complete availability with all micro‐organisms was reached. It is suggested that the availability of essential amino acids in the proteins may be determined microbiologically after total enzymic hydrolysis by papain, leucine aminopeptidase and prolidase. By this method the proteins of beef muscle freeze‐dried and stored for 4 years, and those of meat bone meal and blood meal were analyzed.