Mobilization of seed protein reserves.
The mobilization of seed storage proteins upon seed imbibition and germination is a crucial process in the establishment of the seedling. Storage proteins fold compactly, presenting only a few vulnerable regions for initial proteolytic digestion. Evolutionarily related storage proteins have similar three-dimensional structure, and thus tend to be initially cleaved at similar sites. The initial cleavage makes possible subsequent rapid and extensive breakdown catalyzed by endo- and exopeptidases. The proteolytic enzymes that degrade the storage proteins during mobilization identified so far are mostly cysteine proteases, but also include serine, aspartic and metalloproteases. Plants often ensure early initiation of storage protein mobilization by depositing active proteases during seed maturation, in the very compartments where storage proteins are sequestered. Various means are used in such cases to prevent proteolytic attack until after imbibition of the seed with water. This constraint, however, is not always enforced as the dry seeds of some plant species contain proteolytic intermediates as a result of limited proteolysis of some storage proteins. Besides addressing fundamental questions in plant protein metabolism, studies of the mobilization of storage proteins will point out proteolytic events to avoid in large-scale production of cloned products in seeds. Conversely, proteolytic enzymes may be applied toward reduction of food allergens, many of which are seed storage proteins.
Department of Biological Sciences, State University of New York at Binghamton, Binghamton, NY 13902, USA. annatan@binghamton.edu
Anna L
AL
Tan-Wilson
Karl A
KA
Wilson
D018525:Germination; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010447:Peptide Hydrolases / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D011480:Protease Inhibitors / Q000378:metabolism; D017510:Protein Folding; D021381:Protein Transport; D059748:Proteolysis; D055314:Seed Storage Proteins / Q000378:metabolism*; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism; D012639:Seeds / Q000378:metabolism* / Q000502:physiology; D012995:Solubility; D030262:Soybean Proteins / Q000378:metabolism; D013025:Glycine max / Q000378:metabolism / Q000502:physiology
D010937:Plant Growth Regulators; D011480:Protease Inhibitors; D055314:Seed Storage Proteins; D030262:Soybean Proteins; D010447:Peptide Hydrolases