Communication Dans Un Congrès Année : 2009

Accumulation of polymeric proteins in developing grains of hexaploid wheats in relation with changes in the glutathione thiol-disulfide status

Résumé

It has long been known that the properties of hydrated gluten or wheat flour dough depend on two main types of protein, the glutenins and gliadins. Among these storage proteins, glutenins (polymeric proteins) which are multiple chain polymers in which the individual polypeptides or subunits (HMW-GS and LMW-GS) are linked by disulfide bonds, have been shown to be extremely important in determining rheological properties. Both the amount (TPP) and size distribution of polymeric protein (PPP) have been shown to be important and their contribution to baking performance has been extensively studied and documented throughout the world (1-4). Moreover, a certain amount of these polymers remains unextractable (UPP) in various extracting systems (e.g. acetic acid solution or SDS phosphate buffer) and the proportion of this unextractable polymeric protein (UPP) fraction (among the polymeric proteins) (i.e. polymerization index) is reported to be related to the technological response (5). Regarding the importance of the UPP fraction in breadmaking quality, it seems very important to study its accumulation in the kernel during grain filling. The current study was undertaken to understand more precisely the function of glutathione in developing wheat kernel for the formation of UPP. In fact, glutathione (c-glutamyl-cysteinyl-glycine) which is the predominant non-protein thiol in plants may occur endogenously in wheat flour in the free forms as well as in the form of protein-glutathione mixed disulfides (PSSG). Moreover, the highest PSSG content in the different flour protein fractions was observed for the fraction containing mainly PP (6). The major wheat glutenin subunits residing in the protein body undergo redox change during the development and the maturation of the grain. Indeed, during the cell division and the cell enlargement phase, glutenin subunits and particularly LMW-GS have a large amount of free SH groups and become oxidized during grain dehydration which coincided with the formation of UPP. Moreover, during this important phase (after 33 DAA), glutathione reductase (GR) activity declines, the ratio of GSSG to GSH increases and PSSG occurs. Approximately 85% of PSSG in mature wheat grains are represented by polymeric protein conjugated to glutathione (PP-S-S-G). As asymmetrical flow field flow fractionation–multi-angle laser light scattering (AFFFF–MALLS) analysis showed, the PP-S-S-G formation during the grain desiccation can induce an increase in the SDS solubility of the polymeric protein by reducing both their molecular weight distribution and the branching of these aggregates. According to our results we speculate that glutathione may play a crucial role in controlling the degree of polymerisation of the polymeric protein, which has been shown to be extremely important in determining baking performance.

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Dates et versions

hal-04600421 , version 1 (04-06-2024)

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  • HAL Id : hal-04600421 , version 1

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Thierry Aussenac. Accumulation of polymeric proteins in developing grains of hexaploid wheats in relation with changes in the glutathione thiol-disulfide status. Xth International Gluten Workshop, INRA Clermont-Ferrand, Oct 2009, Clermont-Ferrand, France. ⟨hal-04600421⟩
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