Effects of alkali on glycoproteins. .beta.-Elimination and nucleophilic addition reactions of substituted threonyl residues of antifreeze glycoprotein

Abstract

The oils from all the chemically treated oranges contained less of the major terpene alcohol, linalool, and more of the aldehydes asinensal, citronellal, and dodecanal and of the sesquiterpene hydrocarbon valencene than the oil from control fruit. An increase in -sinensal, which has an odor threshold in water of only 3.8 ppb (Ahmed and Dougherty, 1973), may be significant since its aroma resembles that of overripe citrus.When control and treated oils from well-matured Valencia were compared, only minor quantitative differences in major constituents were observed. In quantitative composition the oils from control and treated, well-matured Valencia oranges were similar to the oil from the treated, barely-mature fruit. This finding suggests an acceleration of the maturing process when barely-mature oranges are sprayed with rind-injuring abscission agents, but not when well-matured fruit are similarly treated.

Chemistry, Biochemistry, Nutrition, and Microbiology of Lysinoalanine, Lanthionine, and Histidinoalanine in Food and Other Proteins

“…Liardon et al (1991) describe a procedure to quantitate these two LAL isomers by GC/ MS after protein hydrolysis and derivatization to diastereomeric N(O,S)-perfluoropropionyl isopropyl esters (Figure 3). Kikutani et al, 1982cereal products 200-390 Antilla et al, 1987Hasegawa et al, 1987;Sternberg and Kim, 1977;Struthers et al, 1980 chicken meat 370 Sternberg andKim, 1977 eggs 160-1820 Fritsch and Klostermeyer, 1981a,b;Hasegawa et al, 1987;Murase and Goto, 1977;Raymond, 1980;Sternberg et al, 1975a,b;Sternberg and Kim, 1977gelatin 250 Fujimoto et al, 1984infant formulas, dry 150-920 Antilla et al, 1987Bellemonte et al, 1987infant formulas, liquid 160-2120Bellemonte et al, 1987Langhendries et al, 1992;Pfaff, 1984;Pompei et al, 1987meat products 140-540 Hasegawa et al, 1987milk powders 150-1620Aymard et al, 1978Fritsch and Klostermeyer, 1981a,b;Hasegawa et al, 1987;Sternberg and Kim, 1977noodles, Chinese 480 Hasegawa et al, 1987skipjack, dry 410 Kikutani et al, 1984sodium caseinate 430-6900 Aymard et al, 1977Lee et al, 1977;Moret et al, 1994; Kim, 1977 soy protein isolate 370-1300 Aymard et al, 1978;Kim, 1975 whipping agents 6500-53150 Fritsch and...…”

“…CHEMISTRY Mechanisms of LAL Formation. Figure 1 depicts a postulated mechanism of LAL formation (Asquith and Otterburn, 1977;Friedman, 1973Friedman, , 1977aFriedman, ,b, 1978aFriedman and Noma, 1986;Lee et al, 1977;Maga, 1984;Patchornik and Sokolovsky, 1964;Feeney, 1977, 1983). The mechanism involves an OHioncatalyzed transformation of the -NH 2 group of lysine to a LAL side chain via elimination and cross-link formation.…”

Evidence for lysinomethylalanine formation in model systems

“…The formation of LMeAL in proteins has been supposed by Lee et al (1977). These authors, however, could not…”

Chemical and Enzymatic Protein Modifications and Functionality Enhancement

“…When a protein is heated at alkaline pH, cystine, O-phosphorylserine, or O-glycosylserine become dehydroalanine, and O-phosphorylthreonine and O-glycosylthreonine become β-methyldehydroalanine by the β-elimination reaction (Lee et al 1977 1999). Then, these β-unsaturated carbonyl compounds proceed to cross-link with the thiol group of a cysteine residue, forming lanthionine and β-methyllanthionine from dehydroalanine and β-methyldehydroalanine, respectively.…”