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首页> 外文期刊>Journal of Plant Physiology >Competitive inhibition of phosphoglucose isomerase of apple leaves by sorbitol 6-phosphate
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Competitive inhibition of phosphoglucose isomerase of apple leaves by sorbitol 6-phosphate

机译：山梨糖醇6-磷酸竞争性抑制苹果叶片磷酸葡萄糖异构酶

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摘要

Apple leaf cytosolic phosphoglucose isomerase (PGI, EC 5.3.1.9) was purified to an apparent homogeneity with a specific activity of 2456 units/mg protein, and chloroplastic PGI was partially purified to a specific activity of 72 units/mg protein to characterize their biochemical properties. These two isoforms showed differential responses to heat treatment; incubation at 50 pC for 10 min resulted in a complete loss of the chloroplastic PGI activity, whereas the cytosolic PGI only lost 50% of its activity. Apple cytosolic PGI is a dimeric enzyme with a molecular mass of 66 kDa for each monomer. The activity of both isoforms was strongly inhibited by erythrose 4-phosphate (E4P) with a Ki of 1.2 and 3.0 oM for the cytosolic PGI and chloroplastic PGI, respectively. Sorbitol 6-phosphate (Sor6P), an intermediate in sorbitol biosynthesis, was found to be a competitive inhibitor for both cytosolic and chloroplastic PGIs with a Ki of 61 and 40 oM, respectively. PGIs from both spinach and tomato leaves were also inhibited by Sor6P in a similar manner. The possible physiological significance of this finding is discussed.
机译：将苹果叶片胞质磷酸葡萄糖异构酶（PGI，EC 5.3.1.9）纯化至表观同质性，比活性为2456单位/ mg蛋白，并将叶绿体PGI部分纯化至比活性为72单位/ mg蛋白，以表征其生化特性属性。这两种同工型对热处理的反应不同。在50 pC下孵育10分钟导致叶绿体PGI活性完全丧失，而胞质PGI仅丧失其活性的50％。苹果的胞质PGI是一种二聚体酶，每个单体的分子量为66 kDa。胞浆PGI和叶绿体PGI的四磷酸赤藓糖（E4P）的Ki分别为1.2和3.0 oM，强烈抑制了这两种同工型的活性。发现山梨糖醇生物合成的中间体磷酸6-山梨糖醇（Sor6P）是胞质PGI和叶绿体PGI的竞争性抑制剂，Ki分别为61和40 oM。菠菜和番茄叶片的PGI也以类似的方式被Sor6P抑制。讨论了这一发现可能的生理意义。

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