QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lee, H. S. Articles by Feeney, R. E. Search for Related Content PubMed PubMed Citation Articles by Lee, H. S. Articles by Feeney, R. E.

Effect of Reductive Alkylation of the -Amino Group of Lysyl Residues of Casein on Its Nutritive Value in Rats^1,2,3,

Departments of Food Science and Technology and Nutrition, University of California, Davis, California 95616

Casein -aminolysyl residues were converted to the methyl (and dimethyl), isopropyl or cyclopentyl derivatives in high yield with formaldehyde, acetone or cyclopentanone, respectively, in the presence of sodium borohydride. When incorporated into diets at 10% as the sole protein source, the chemically modified caseins failed to support growth of young rats. Methyl casein did, however, support limited growth after about 5 days. Plasma threonine levels increased and lysine levels decreased markedly in rats fed the alkyl caseins. The respective alkyllysine derivatives were present in plasma and urine. In another experiment, nearly normal or normal growth was obtained by feeding lysine-supplemented methyl or isopropyl casein, respectively. A preparation of partially methylated casein, containing approximately equal amounts of monomethyl- and dimethyllysines, supported normal rat growth. These results demonstrate that lysine deficiency was produced by feeding highly alkylated caseins. Digestibility of the chemically modified caseins in vivo was not affected, although in vitro studies with trypsin and -chymotrypsin showed lowered digestibility. Since no apparent toxicity was observed, limited methylation of food proteins may be useful for protection of lysyl residues against deteriorative reactions during processing and storage.

KEY WORDS: • casein modification • lysine deficiency • plasma amino acids • -N-methyllysine • -N,N-dimethyllysine • -N-isopropyllysine

¹ Supported in part by FDA Grant FD-00568-02.

² Taken in part from thesis of H.S.L. to be submitted to the Graduate Division of the University of California, Davis, in partial fulfillment of requirements for the Ph.D. degree in Nutrition. A preliminary report of this work was presented at the 61st Annual Meeting of Federation of American Societies for Experimental Biology Chicago, Ill. (1977) Federation Proc. 36, 1179 (Abstr. #4805).

³ Address reprint requests to R. E. Feeney, Department of Food Science and Technology, 3450 Chemistry Annex.

⁴ Present address: The Quaker Oats Company, Barrington, Illinois 60010.

Manuscript received 27 June 1977.