Wheat thiol group

Koehler, P. 2003. Effect of acid in dough Reduction of oxidised glutathione with reactive thiol groups of wheat glutelin. J Agric Food Chem 51 4954-4959. 

The ascorbic acid is oxidized by ascorbic acid oxidase in the flour dough to dehydroascorbic acid. In turn, the reduction of dehydroascorbic acid is coupled with the oxidation of protein thiol groups by the enzyme dehydroascorbic acid reductase known to be in wheat (133). 

Several models for the structure of wheat glutenin have been proposed. One of the earliest molecular models was that of Ewart [62]. He subsequently modified the model. Ewart s latest model shows one disulfide bond between two adjacent polypeptide chains of glutenins, which consist of linear polymers. Ewart pointed out that the rheological properties of dough are dependent on the presence of theologically active disulfide bonds and thiol groups as well as on secondary forces in the concatenations [63]. 

Burnouf and Bietz [19] first explored methods for solubilization, stabilization, and RP-HPLC analysis of wheat glutenin. For optimal separations, glutenin was extracted with solutions containing 8M urea or 6M guanidine hydrochloride and 5% 2-mercaptoethanol or 0.1% DTT resulting thiol groups were stabilized by alkylation with 4-vinylpyridine acidified reaction mixtures could then be analyzed directly by RP-HPLC. 

P Amylases.—The thiol groups of the j8-amylase from wheat reacted instantly with 4-chloromercuribenzoate and A -ethylmaleimide in the absence of a substrate. Derivatization almost completely abolished the enzymic activity, and the kinetics indicated that inhibition by the mercury compound is non-competitive. Inhibition by these reagents was considerably less in the presence of a substrate, since the enzyme undergoes an induced conformational change that renders the internal thiol groups inaccessible. The free thiol groups of the enzyme were divided into two types in these reactions two groups on the molecular surface that play no part in the catalysis, and two in the interior that do. 

Koehler P. Effect of ascorbic acid in dough reaction of oxidized glutathione with reactive thiol groups of wheat gluteline. Journal of Agricultural and Food Chemistry, 51 4954-4959 (2003). 

Wheat cultivars differ in the content of their thiol and disulfide groups (Table 15.40). This implies that the stabUity of a dough may be strongly influenced by a SH/SS exchange between a low molecular weight SH-peptide and gluten proteins. This also implies that a positive correlation... 

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