Structural Modifications of Amaranth Proteins During Germination

Abstract

Amaranth storage proteins begin to be hydrolyzed immediately following the completion of germination. Albumins and globulins (7S globulin, 11S-globulin and globulin-p) were formerly modified, and glutelins, the most aggregated fraction, later. Globulins mobilization starts with the proteolysis of the 7S like-globulin polypeptides and the propolypeptide and acid (A) polypeptides of 11S-globulin and globulin-p. This pattern of 11S-globulin mobilization is accounted by the structural model with propolypeptide and A polypeptides exposed to the outside. Amaranth globulin molecules showed minor changes in their sizes in spite of having some of their polypeptides cleaved. Although globulin-p is more aggregated than 11S-globulin, it showed greater conformational changes. Considering the high susceptibility of the propolypeptide to enzymatic hydrolysis, the higher content of this polypeptide in globulin-p molecules might explain their higher structural changes. According to the results, the order of mobilization of storage proteins depends on the combination of two structural characteristics, the state of aggregation and the presence on the surface of polypeptides susceptible to cleavage.