The inhibition by physiological orthophosphate concentrations of hydrolytic and synthetic activities of liver glucose 6-phosphatase.
The inhibition by physiological orthophosphate concentrations of hydrolytic and synthetic activities of liver glucose 6-phosphatase.
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生理正磷酸盐浓度对肝葡萄糖 6-磷酸酶的水解和合成活性的抑制。
DOI：
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发表时间：
1969
影响因子：
4.8
通讯作者：
R. C. Nordlie
中科院分区：
文献类型：
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作者：
A. L. Vianna;R. C. Nordlie
本文详细研究了正磷酸盐对大鼠肝葡萄糖6-磷酸酶（EC 3.1.3.9）葡萄糖6-磷酸水解酶和无机焦磷酸-葡萄糖磷酸转移酶活性的抑制作用。在研究的整个pH值范围内（pH 5.0至7.5（水解酶）或pH 5.0至6.5（磷酸转移酶）），均观察到这两种活性的显著抑制。洗涤剂十六烷基三甲基溴化铵（溴化十六烷基三甲铵）和lysolopropane显着降低Ki值与两个活动的Pi。例如，在pH 7.5下，在不存在去污剂的情况下注意到Ki值为18 mm，而用西曲溴铵初步处理微粒体至0.05%（w/v），将该值降低至2.0 mm，在测定混合物中加入0.4 mm的溶血素，导致Ki下降至4.6 mm。由于去污剂对Km的伴随修饰作用程度不同，值为底物，净抑制葡萄糖6-磷酸水解酶活性的Pi是相当广泛的增强洗涤剂比磷酸转移酶活性。无论是在没有和存在的洗涤剂，抑制动力学竞争相对于葡萄糖6-磷酸和焦磷酸和非竞争性相对于葡萄糖的磷酸转移酶反应。在磷酸水解酶活性抑制研究中，正磷酸盐与三磷酸腺苷、碳酸氢盐和焦磷酸盐的相互作用具有相互竞争的性质。一个生理上重要的监管作用，通过其对这种酶的活性的影响，建议在这些实验观察的基础上。
Abstract The inhibition by orthophosphate of glucose 6-phosphate phosphohydrolase and inorganic pyrophosphate-glucose phosphotransferase activities of rat liver glucose 6-phosphatase (EC 3.1.3.9) has been studied in detail. Significant inhibitions of both activities were noted over the entire range of pH values studied—pH 5.0 to 7.5 (hydrolase) or pH 5.0 to 6.5 (phosphotransferase). The detergents cetyltrimethylammonium bromide (Cetrimide) and lysolecithin significantly lowered Ki values for Pi with both activities. For example, at pH 7.5, a Ki value of 18 mm was noted in the absence of detergents, while preliminary treatment of microsomes with Cetrimide, to 0.05% (w/v), reduced this value to 2.0 mm, and inclusion of 0.4 mm lysolecithin in assay mixtures led to a decrease in Ki to 4.6 mm. Because of differences in the extents of accompanying modifying effects of detergents on Km values for substrates, net inhibition by Pi of glucose 6-phosphate phosphohydrolase activity was considerably more extensively potentiated by detergents than was that of phosphotransferase activity. Both in the absence and presence of detergents, inhibitions were kinetically competitive with respect to glucose 6-phosphate and pyrophosphate and non-competitive with respect to glucose in the phosphotransferase reaction. The mutually competitive nature of interactions of orthophosphate with adenosine triphosphate, bicarbonate, and pyrophosphate noted in inhibition studies carried out with phosphohydrolase activity also was shown. A physiologically significant regulatory role for Pi, through its effects on activities of this enzyme, is suggested on the basis of these experimental observations.