Amino acid analyzer studies of the products of peroxide oxidation of cystine, lanthionine, and homocystine

Abstract

Mixtures of several sulfur amino acid oxidation products were formed in the oxidation of cystine, lanthionine, or homocystine by aqueous hydrogen peroxide in the presence of hydrochloric acid. After 10 min at 100 "C in 6% HzOz and 0.8 N HC1, cysteic acid was the main oxidation product of cystine; lanthionine sulfoxide, lanthionine sulfone, and unidentified products were also formed. In a similar oxidation of lanthionine, lanthionine sulfoxide was the most abundant product; cysteic acid, lanthionine sulfone, and unidentified products were also formed. An identical oxidation of homocystine afforded homolanthionine sulfoxide as the main product; homolanthionine sulfone and homocysteic acid were also formed. When homocystine was oxidized at 50 "C, homolanthionine was the principal product. However, when the HC1 concentration was increased to 4.8 N, homocysteic acid and homolanthionine sulfone were the main products. Sulfoxide produds were distinguished by reduction with dimethyl sulfide in the presence of HC1. Thus, they were converted into their corresponding sulfides and shifted to new chromatographic locations. These desulfurizations by hydrogen peroxide in the presence of HC1 are discussed in relation to known chemical changes of amino acids, including lanthionine formation, which occur in alkali-treated foods and to the use of peroxide in food technology.

Opinion of the Scientific Panel on food additives, flavourings, processing aids and materials in contact with food (AFC) related to Treatment of poultry carcasses with chlorine dioxide, acidified sodium chlorite, trisodium phosphate and peroxyacids

“…Lanthionine generates lanthionine sulphoxide, lanthinine sulphone and some unidentified products. The oxidation of homocystine generates homolanthionine sulfoxide as main product and homolanthionine sulphone and homocysteic acid (Lipton et al, 1977). Reduced glutathione can be oxidised by hydrogen peroxide.…”

Peroxide oxidation products of homocystine and lanthionine

“…These chemical losses of sulfur from disulfide amino acids are of interest because lanthionine is formed in heated proteins (Hurrell et al, 1976). In the present study, peroxide oxidations were on a larger scale so that products could be purified and the assigned structures (Lipton et al, 1977) and DL-homolanthionine were isolated from peroxide oxidation of DL-homocystine, and meso-lanthionine sulfone was isolated from peroxide oxidation of meso-lanthionine. Peroxide oxidation products of the thioether amino acids S-methyl-L-cysteine and S-ethyl-L-cysteine were studied on the amino acid analyzer.…”

“…Peroxide oxidation of the sulfur amino acids cystine, lanthionine, and homocystine formed products that varied with reaction conditions, particularly hydrochloric acid concentration (Lipton et al, 1977). An especially interesting feature of the peroxide oxidation of the disulfide amino acids was the loss of 1 mol of sulfur.…”

“…The formation Protein Nutrition Laboratory, Nutrition Institute, Federal Research, Science and Education Administration, Agricultural Research Center-East, U.S. Department of Agriculture, Beltsvilie, Maryland 20705. of homolanthionine sulfoxide and sulfone by peroxide oxidation of homocystine was first reported by Clopath and McCully (1976). Homocystine oxidation was further studied and the analogous formation of lanthionine sulfoxide and sulfone from peroxide oxidation of cystine was reported (Lipton et al, 1977). These chemical losses of sulfur from disulfide amino acids are of interest because lanthionine is formed in heated proteins (Hurrell et al, 1976).…”

“…EXPERIMENTAL SECTION Materials. Amino acids and other chemicals were from the sources reported (Lipton et al, 1977) with two additions. S-Methyl-L-cysteine and S-ethyl-L-cysteine were from Sigma Chemical Co.…”