The formation, isolation and importance of isopeptides in heated proteins.
The separation and resolution of the isopeptides Nepsilon (gamma-L-glutamyl)-L-lysine and Nepsilon (beta-aspertyl)-L-lysine, formed in heated proteins, has been successfully achieved. The method demands a well characterised ion-exchange column and the use of pH 3.40 lithium citrate buffer (O.2N Li+). Due to variations in particle size and percentage crosslinkages in the ion-exchange resin a computer assisted buffer gradient system has been developed. This system affects resolution of both isopeptides in 7h. The use of leucyl-glycine as an internal standard facilitates quantitative estimation of the isopeptides. This separative method has been used to analyse a series of heated protein samples and to estimate the quantities of isopeptides formed. The ability of a protein to form isopeptides links is discussed as well as the implication of such links on the reactivity and digestibility of proteins.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001224:Aspartic Acid / Q000302:isolation & purification; D002021:Buffers; D055598:Chemical Phenomena; D002621:Chemistry; D004044:Dietary Proteins; D004151:Dipeptides / Q000302:isolation & purification; D005223:Fats; D005971:Glutamates / Q000302:isolation & purification; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008094:Lithium; D008239:Lysine / Q000302:isolation & purification; D008433:Mathematics; D008722:Methods; D011506:Proteins; D051381:Rats; D013229:Stearic Acids
D000596:Amino Acids; D002021:Buffers; D004044:Dietary Proteins; D004151:Dipeptides; D005223:Fats; D005971:Glutamates; D011506:Proteins; D013229:Stearic Acids; D001224:Aspartic Acid; D008094:Lithium; D008239:Lysine