Formation of Proteinase Inhibitors in Developing Barley Grain

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Abstract
Assays have been made of the activities of trypsin inhibitors and Aspergillus‐proteinase inhibitors in developing grains of barley (Hordeum vulgare L.) grown under controlled conditions. Trypsin inhibitor activity appeared early in the development, reaching a near‐maximal value 24 days after anthesis, but Aspergillus‐proteinase inhibitors were synthesized quite late in the development. A half‐maximal value was attained about 25 days subsequent to anthesis. The corresponding half‐maximal value for all the proteins synthesized was about 16 days.The trypsin inhibitor present in developing grains appeared to be immunologically identical with the endospermal inhibitor in mature grains.The concentrations of Aspergillus‐proteinase inhibitors varied between different cultivars of barley. Moreover, each cultivar displayed an almost linear relationship between inhibitor activity and the increasing content of total protein. Great differences between different cultivars were also observable with regard to trypsin inhibitor activities. However, the activities in each cultivar were constant, regardless of the total protein content.The author is greatly indebted to Dr. Juhani Mikola for many helpful discussions during the course of the work, and for several valuable suggestions in regard to the manuscript. I also wish to thank Mrs. Marja‐Leena Niku‐Paavola, Lic. Phil., for valuable help in the immunodiffusion experiments, and Miss Outi Karkkainen for skilful technical assistance. This work was supported by grants from the Emil Aaltonen Foundation and from the E. J. Sariola Foundation.