Sep 1, 1975

The participation of methionine and cysteine in the formation of bonds resistant to the action of proteolytic enzymes in heated casein

The British Journal of Nutrition
D PieniaźekH Kunachowicz

Abstract

1. The influence of temperature, moisture content and the presence of glucose on the level of available methionine and cysteine in casein was studied. 2. Differences between total and available methionine and cysteine contents of heated casein (90 degrees for 24 h) were determined by an in vitro method. The maximum losses in total and available methionine content were 22 and 51% respectively. The losses in total and available cysteine content were 24 and 100% respectively. 3. The results indicated that for heated casein the release of amino acids by proteolytic enzymes was less complete than for native casein. 4. The results of rat growth assays suggested that diets containing oxidized casein are less well utilized by rats than those containing native casein. The decrease in body-weight of rats receiving the diets containing oxidized casein could be counteracted by the addition of methionine and 20 g unoxidized casein/kg diet. 5. There was a lower level of some available amino acids (determined after enzymic hydrolysis using pancreatopeptidase E (EC 3-4-4-7), leucine aminopeptidase (EC 3-4-I-I) and prolidase (EC 3-4-3-7)), including those essential for the rat, in oxidized casein as compared with native casein. 6. Cysteic acid,...Continue Reading

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Mentioned in this Paper

Casein allergenic extract
Diet
Caseins
Cysteic Acid
Amino Acids, I.V. solution additive
Complex (molecular entity)
Peptide Hydrolases
Methoxyleucine Aminopeptidase
Leucine Aminopeptidase
X-Pro dipeptidase

About this Paper

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