Specific Reduction ofWheatStorage Proteins by Thioredoxin h1

Gliadins andglutenins, themajorstorage proteins ofwheat endosperm (Triticum durum, Desf. cvMonroe), werereduced in vitro bytheNADP/thioredoxin system (NADPH, NADP-thioredoxin reductase andthioredoxin; inplants, thehtype) fromeither the samesource orthebacterium Escherichia coli. A morelimited reduction ofcertain members ofthese protein groups wasachieved withthereduced formofglutathione orglutaredoxin, aprotein knowntoreplace thioredoxin incertain bacterial andmammalian enzymesystems butnotknowntooccurinhigher plants. Endosperm extracts contained theenzymes necessary toreduce NADP bytheoxidative pentose phosphate pathway (hexokinase, glucose6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase). Thegliadins andglutenins werealsoreduced invivoduring germination-an event that accompanied their proteolytic breakdown.Theresults suggest thatthioredoxin, reduced byNADPH generated viatheoxidative pentose phosphate pathway, functions asasignal ingermination toenhance metabolic processes such as themobilization ofstorage proteins and, asfoundearlier, the activation ofenzymes.