Document Detail

The use of Escherichia coli mutants to measure the bioavailability of essential amino acids in foods.
MedLine Citation:
PMID:  2652134     Owner:  NLM     Status:  MEDLINE    
The beta-galactosidase-based assay for lysine developed by Tuffnell & Payne was used to measure the bioavailabilities of cyst(e)ine, methionine, threonine and tryptophan in pronase digests of 17 foods. The digests were assayed by estimating the beta-galactosidase synthesis responses of five Escherichia coli mutants, each requiring one of the respective amino acids for protein synthesis. Deletion mutants were used whenever possible in order to ensure strain stability. Single digests of each food were assayed with 3 or 4 separate cultures of each mutant and the results were compared with those from the corresponding chemical assay. Omitting the anomalously low values for one food, the rank correlation coefficients of the bio- and chemo-assay values were 0.61 (cysteine), 0.91 (lysine), 0.95 (methionine), 0.64 (threonine) and 0.85 (tryptophan). Mean (+/- S.D.) relative amino acid bioavailabilities (casein = 100%) for the 17 foods were: cysteine, 53 +/- 23; lysine, 90 +/- 10; methionine, 95 +/- 18; threonine, 89 +/- 13; and tryptophan, 89 +/- 25. The cysteine mutant appeared to give unusually low bioavailability values except for the milk products. These amino acid mutants afford a rapid method for assaying the bioavailabilities of at least four of the five amino acids studied.
A D Hitchins; F E McDonough; P A Wells
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  Plant foods for human nutrition (Dordrecht, Netherlands)     Volume:  39     ISSN:  0921-9668     ISO Abbreviation:  Plant Foods Hum Nutr     Publication Date:  1989  
Date Detail:
Created Date:  1989-06-08     Completed Date:  1989-06-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8803554     Medline TA:  Plant Foods Hum Nutr     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  109-20     Citation Subset:  IM    
US Dept. of Agriculture, Beltsville Human Nutrition Research Center, MD 20705.
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MeSH Terms
Amino Acids, Essential / analysis,  metabolism*
Biological Assay / methods*
Escherichia coli*
Fabaceae / metabolism
Food Handling
Nutritive Value
Plants, Medicinal
Reg. No./Substance:
0/Amino Acids, Essential

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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