Cereal Chem 40:704 - 716.  |  VIEW ARTICLE

Reactions of Flour Protein Sulfhydryl with N-Ethylmaleimide and Iodate.

R. Tkachuk and I. Hlynka. Copyright 1963 by the American Association of Cereal Chemists, Inc. 

Chemical evidence is presented that the identity of flour sulfhydryl(-SH) is due to cysteine-containing proteins. Approximately one-half of the flour -SH reacts readily with N-ethylmaleimide (NEMI), the remainder only in the presence of 8M urea. Flour -SH is involved in the improver reaction, since there was no -SH available for reaction with NEMI in sufficiently mixed doughs previously treated with iodate. With L-cysteine, NEMI forms two products or isomers, which are slowly hydrolyzed to S-succinyl-L-cysteine and ethylamine in 6N hydrochloric acid at 120C., the complete hydrolysis requiring 60 hr. With GSH, NEMI forms one product plus ethylamine. The GSH-NEMI product on a 22-hr. hydrolysis yielded S- succinyl-L-cysteine, glycine, and glutamic acid. Wheat proteins treated with NEMI behaved analogously to GSH..