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Distribution of glutathione and its metabolic intermediates in flours and protein fractions. WEILI LI, S.
S. J. Bollecker, A. A. Tsiami, C. Stathopoulos, and J. D. Schofield. The University of Reading, Department
of Food Science and Technology, Reading RG6 6AP, UK.
Reliable and convenient HPLC methodology has been established to
measure not only the levels of glutathione but also the levels of cysteine and the metabolic intermediates of
glutathione (gamma-glutamylcysteine and cysteinylglycine) in free reduced, oxidised and protein bound
forms in flour and protein fractions. Using this method, the levels of those compounds have been
investigated in flour, gliadin and glutenin fractions, as well as protein fractions prepared by a salt
precipitation technique, from the strong UK bread making wheat variety, Hereward. No clear-cut
relationship was found between the flour quality and the levels of the free compounds amongst a set of UK
wheat lines/varieties. However, it was interesting to observe that the level of the protein bound compounds
in glutenin from cv. Hereward was highest in the glutenin polymer fraction of greatest molecular weight as
determined by Flow Field-Flow Fractionation and Multi Angle Laser Light Scattering. This same fraction
also had the most elastic properties as determined by small deformation oscillatory rheometry. Gliadin was
prepared by ethanol extraction and purification by gel filtration chromatography to remove none gliadin
compounds, such as small glutenin polymer. Such purified gliadin still contained small but significant
amounts of protein bound glutathione, cysteine. The results may indicate that glutathione and other
metabolic intermediates play a crucial role in controlling the degree of polymerisation of the glutenin
polymers during protein synthesis and deposition. Gliadin components also appear to be capable of forming
mixed disulphide with the various sulphydryl compounds analysed.
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