Covalent attachment of poly(L-methionine) to food proteins for nutritional and functional improvement

Abstract

468.Sarwar, G.; Christensen, D. A.; Finlayson, A. J.; Friedman, M.; Hackler, L. R.; Mackenzie, S. L.; Pellett, P. L.; Tkachuk. R. J . Food. Sci. 1983, 48, 526. 22, 437. Schmidtborn, H.; Spindler, M. Feedstuffs 1982,54 (42), 43. Schmidtborn, H.; Spindler, M. Kochseder, J.; Preining, F. Schram, E.; Dustin, J. P.; Moore, S.; Bigwood, E.Methionine, the first limiting essential amino acid of many plant proteins, has been covalently attached to casein and @-lactoglobulin by using the N-carboxyanhydride method. Introduction of as much amino acid as 30% of protein weight led to the formation of polymethionine chains linked to the lysyl residues through isopeptide bonds. Under polymerization conditions at pH 6.5, attachment efficiency was close to 80% and about 40% of the lysyl residues were acylated. In contrast, successive addition of reagent at pH 10.2 reduced the efficiency to 25-30% while all the t-amino groups were modified. Important changes in solubility properties were observed with polymethionylcasein and to a lesser extent with methionylcasein. "In vitro" digestion studies, performed with bovine a-chymotrypsin and trypsin at pH 8.2 and 38 "C, resulted in a significant decrease of hydrolysis of casein derivatives that was correlated with chain length and distribution of methionine polymers as well as conformational changes as indicated by fluorescence studies. Polymerization of amino acids onto food proteins may be a valuable procedure for improving their nutritional and functional properties.

Effect of the attachment of valine residues on the physicochemical and functional properties of bovine serum albumin

“…It was therefore clear that the attachment of valine at pH 6.5 occurred at fewer sites but that slightly longer polyvalyl chains were attached in sample VALl compared with modification at pH 10.2 resulting in VAL2. This was comparable to literature values (Konigsberg and Becker 1959;Gaertner and Puigserver 1984).…”

“…These results also indicated that modification caused a variety of products as bands were broad. This phenomenon has been quoted previously (Gaertner and Puigserver 1984). The increase in negative charge on the protein caused by the conversion of &-amino groups to terminal a-amino groups would be expected to cause increased mobility in this gel system and the results confirmed this.…”

“…Amino acid attachment was carried out according to Gaertner and Puigserver (1984) using a 2:3 molar ratio of amino groups of Ncarboxyvaline anhydride. The reaction was carried out at pH 6.5 and at pH 10.2 to give samples VAL1 and VAL2 respectively.…”

DEVELOPMENT of KINETIC MODELS FOR METHIONINE DEGRADATION IN FORTIFIED SOYBEAN MODEL SYSTEMS

“…The nutritional quality of soy protein, although limited by its content of methionine, may be enhanced by addition of this amino acid (Haj6s et al 1988;Gaertner and Puigserver 1984;Chuah et al 1983;Fomon et al 1979;Graham et al 1969;Panemangalore 1964). However, added free methionine may be inactivated or at least partially destroyed during processing or storage, resulting in less nutritionally available methionine.…”

Transglutaminase-catalyzed incorporation of lysine oligomers into casein

“…However, when macromolecular substrates instead of rather short synthetic peptide substrates were used, the main controlling factor for the glutamine substrate specificity of transglutaminase remained poorly understood. Chemical methods have been developed for the covalent attachment of amino acids, particularly methionine, and polyamino acids to proteins to improve their nutritional value (Puigserver et al, 1978;Gaertner and Puigserver, 1984) as well as of polylysine for enhancing their cellular uptake (Shen and Ryser, 1978). We felt it important to explore enzymatic methods for preparing protein derivatives containing a number of lysine oligomers covalently attached to some of the glutamine residues.…”