Incorporation of radioactive molybdenum into protein during nitrate reductase formation and effect of molybdenum on nitrate reductase and diaphorase activities of spinach (Spinacea oleracea L.)

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概要

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• Spinach plants grown without molybdenum lack nitrate reductase and when plants are deprived of nitrate existing activity is lost. Transfer of molybdenum-deficient plants to a solution containing (NH_4)_2^<99>MoO_4, or nitrate-starved plants to NaNO_3 Solution induced enzyme activity in 24 hr. After purification by selective adsorption, precipitation and disc electrophoresis, the protein from molybdenum-deficient plants given ^<99>Mo showed radioactivity only where nitrate reductase was revealed on the acrylamide gel. Molybdenum was similarly selectively concentrated into the enzyme as a result of induction by nitrate in plants grown with sub-optimal molybdenum supply in order to minimize effects of isotope dilution on measurement of ^<99>Mo incorporation. There was no exchange in vitro between ^<99>Mo and purified active enzyme in the resting state over 18 hr at 4℃, or with functioning enzyme held at room temperature for 24 hr. There was evidence either for possible in vivo exchange of ^<99>Mo and enzyme bound Mo or for slight synthesis of fresh enzyme under conditions of net loss of enzyme in nitrate starved plants. Five NADH_2 and two NADPH_2 reactive diaphorases which could be separated by electrophoresis were present in extracts. Only one of these having strong NADH_2 and weak NADPH_2 activity was directly associated with nitrate reductase. The same complex also showed the only benzyl viologen (BV・) reactive nitrate reductase. Nitrate reductase in spinach is therefore considered to be a molybdenum-dependant and molybdenum-containing protein in which NADH_2 (with weak NADPH_2) and BV・ electron donor functions and diaphorase/reductase activities remain closely associated during purification and electrophoresis. The techniques provide a simple means for the production and purification of enzyme containing radioactively labelled Mo applicable to investigations on the structure of the enzyme.

• 日本植物生理学会の論文
• 1971-08-00

著者

• Hewitt E.j.

  Long Ashton Research Station University Of Bristol

• NOTTON B.

  Long Ashton Research Station, University of Bristol

関連論文

• Incorporation of radioactive molybdenum into protein during nitrate reductase formation and effect of molybdenum on nitrate reductase and diaphorase activities of spinach (Spinacea oleracea L.)
• COMPARATIVE EFFECTS SOME ANTIMETABOLITES ON RIBONUCLEIC ACID SYNTHESIS AND INDUCTION OF NITRATE REDUCTASE IN CAULIFLOWER LEAF TISSUES

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