Inverse Correlation of Thiol Proteinase with Nitrate Reductase Activities in Barley Leaves |
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| Authors: | Hamano Takashi; Oji Yoshikiyo; Okamoto Saburo; Mitsuhashi Yukimasa; Matsuki Yukio |
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| Institution: | 1Public Health Research Institute of Kobe City Minatozimanaka-cho 4-6, Chuo-ku, Kobe 650, Japan
2Department of Agricultural Chemistry, Faculty of Agriculture, Kobe University Rokkodai-cho 1-1, Nada-ku, Kobe 657, Japan |
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| Abstract: | Experiments conducted to determine the effects of leupeptin,a specific inhibitor of thiol proteinase, on extractable nitratereductase (NR) activity in leaves of Hordeum distichum duringdarkness revealed that leupeptin (0.01 mg.ml–1) appliedto detached leaves significantly reduced the loss of NR activity.At the same time it also reduced the formation of small cytochromec reductase species, which is a degradation product of NR complex,Upon nitrate induction, extractable NR activity increased butthe content of thiol proteinase decreased. This inverse correlationwas also observed upon transfer of nitrate-grown barley seedlingsto nitrate-free nutrient solution. Furthermore, cycloheximide(0.1 mg.ml–1) treatment of barley seedlings reduced thecontent of thiol proteinase and retarded the loss of NR activityunder noninducing conditions. These results suggest that invivo changes in NR content in leaves of Hordeum distichum arethe result of proteolysis by an endogenous thiol proteinase. (Received May 16, 1985; Accepted July 22, 1985) |
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