大鼠小肠完整细胞和匀浆细胞对蔗糖的水解。pH和底物浓度的影响

A. Dahlqvist, D.L. Thomson
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引用次数: 10

摘要

利用肠道切片和肠道细胞匀浆,在体外研究了大鼠小肠黏膜中蔗糖水解的胞内位点。切片和匀浆的转化酶ph -活性曲线相同。转化酶活性的表观Km明显高于匀浆的表观Km。切片和匀浆的最大速度(V)几乎相同。由于表观Km值的差异,假设在细胞的顶端表面和蔗糖被转化酶水解的位点之间存在屏障。由于屏障减缓了完整细胞中蔗糖向酶的转运,但允许酶位点与液浴和刷状边界之间的pH快速平衡,因此屏障可能位于表面。
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The hydrolysis of sucrose by intact and homogenized cells of rat small intestine. Influence of pH and substrate concentration

The intracellular locus of sucrose hydrolysis in rat small-intestinal mucosa has been studied in vitro using intestinal slices and homogenates of intestinal cells. The pH-activity curves for the invertase of the slices and homogenates were identical. The apparent Km for the invertase activity of the slices was considerably higher than the Km for the homogenates. The maximum velocity (V) for the slices and homogenates was nearly identical. Because of the difference in the apparent Km values, it is postulated that a barrier exists between the apical surface of the cell and the site of hydrolysis of sucrose by invertase. Since the barrier slows the transport of sucrose to the enzyme in the intact cells but permits rapid pH equilibration between the enzyme locus and the fluid bathing and brush border, the barrier may be located superficially.

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