Variation among Species in Light Activation of Sucrose-Phosphate Synthase

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概要

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• Some species exhibit light activation of sucrose-phosphate synthase (SPS) in intact leaves. Twelve species which vary in extent of light modulation of SPS were studied to identify factors which regulate activation of the enzyme in situ. Leaves were harvested in light and darkness, and SPS was assayed under high substrate (Vmax) or limiting substrate conditions (in the presence of th inhibitor inorganic phosphate). The species tested fell into three groups. In some species (Group I; barley and maize) light activation involved an increase in Vmax of the enzyme. In other species (Group II; spinach, swiss chard, sugarbeet, broad bean) light activation had no effect on Vmax but altered certain kinetic properties such that activation was only apparent when SPS was assayed with the limiting substration condition. Significantly, in some species (Group III; soybean, pea, tobacco, Arabidopsis thaliana, cucumber and melon) SPS activity was essentially unaffected by light/dark transitions. Phosphate sequestering agents (mannose or glucosamine) activated SPS in darkness in species which show light modulation (Groups I and II) but not species of Group III which do not light activate. Thus, changes in inorganic phosphate level may be one of the factors which regulate the activation of SPS in situ. In addition, the catalytic activity of SPS from species which exhibit light modulation (Groups I and II) is more strongly inhibited in vitro by inorganic phosphate (an allosteric effector) compared with the enzyme extracted from Group III species, which indicates that certain properties of the enzyme itself may also vary among species. We conclude that species which do not exhibit light activation of SPS in intact leaves lack the mechanism responsible for the covalent modification of enzyme activity (Walker and Huber 1989, Planta, in press) involved in light activation process.

• 日本植物生理学会の論文

著者

• Huber S

  North Carolina State Univ. Nc Usa

• Huber Steven

  Us Department Fo Agriculture Agricultural Research Service And Departments Of Horticultural Science

• Huber Steven

  U.S. Department of Agriculture, Agricultural Research Service, and Departments of Crop Science and B

• Nielsen Tom

  U.S. Department of Agriculture, Agricultural Research Service, and Departments of Crop Science and B

• Huber Joan

  Department of Horticultural Science, North Carolina State University

• Pharr David

  Department of Horticultural Science, North Carolina State University

• Pharr David

  Department Of Horticultural Science North Carolina State University

• Huber Joan

  Department Of Horticultural Science North Carolina State University

• Huber Steven

  U.s. Department Of Agnculture-agncultural Research Service And Departments Of Crop Science And Botan

• Nielsen Tom

  U.s. Department Of Agriculture Agricultural Research Service And Departments Of Crop Science And Bot

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• Biological Significance of Divalent Metal Ion Binding to 14-3-3 Proteins In Relationship to Nitrate Reductase Inactivation
• Variation among Species in Light Activation of Sucrose-Phosphate Synthase
• Root Flooding of Muskmelon (Cucumis melo L.) Affects Fruit Sugar Concentration But Not Leaf Carbon Exchange Rate

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