Reaction of Cystine with Tryptophan under the Conditions of Acid Hydrolysis of Proteins: Mechanism of Action of Cystine

Chemistry, analysis, nutritional value, and toxicology of tryptophan in food. A review

“…In the presence of cystine, tryptophan reacts to give tryptathionine, which is subsequently converted into 2,3-dihydro-2-oxotryptophan, cysteine, and cystine. In the course of this transformation, two compounds are formed, one being bis(2-amino-2-carboxyethyl) trisulfide (Ohta and Nakai, 1979). These data suggest that sulfenic or sulfinic acids, arising from cystine oxidation in the presence of traces of oxygen, are mainly responsible for the loss of tryptophan during the hydrochloric acid hydrolysis of proteins.…”