Occurrence of proteolytic inhibitors in various tissues of barley

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Abstract
The three groups of proteolytic inhibitors present in resting barley grains, namely, trypsin inhibitors, Aspergillus-proteinase inhibitors, and inhibitors of endogenous proteinases, occur in both the embryo and the two endosperm tissues. There are pronounced quantitative differences, however. The three inhibitor activities in the embryo are, respectively, 6-, 0.1-, and 6-fold of those in the endosperm. During germination at 20° all inhibitor activities disappear from the endosperms in 4–5 days. Young rootlets and coleoptiles contain inhibitors of trypsin and Aspergillus proteinase, but these disappear after 4–5 days' germination. However, the trypsin inhibitor content per seedlings remains roughly constant through the whole period. The Aspergillus-proteinase inhibitors, in contrast, exhibit a pronounced increase of activity per seedling. No inhibitor activities were detected in leaves and roots at later stages of growth. The trypsin inhibitor which we have earlier purified from resting grains occurs exclusively in the two endospermal tissues and is immunologically entirely different from the trypsin inhibitors present in embryos and young seedlings.