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首页> 外文期刊>Biochemistry >Influence of alpha-subunits on the high-pressure stability of apo and holo beta 2-subunits in the bienzyme complex tryptophan synthase from Escherichia coli.
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Influence of alpha-subunits on the high-pressure stability of apo and holo beta 2-subunits in the bienzyme complex tryptophan synthase from Escherichia coli.

机译：α亚基对大肠杆菌中双酶复合色氨酸合酶中载脂蛋白和全环β2亚基高压稳定性的影响。

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摘要

At a hydrostatic pressure of up to 2 kbar, the isolated alpha-subunit of tryptophan synthase from Escherichia coli proved to be a stable enzyme by virtue of specific activity as well as UV absorption and fluorescence emission spectra. The protein can therefore be regarded as a suitable effector for the investigation of structure-function relationships in the dimeric beta 2-subunit under the influence of high hydrostatic pressure. Complete deactivation of the beta 2-component in the alpha 2 beta 2 bienzyme complex occurs above 1300 bar (midpoint of transition for alpha apo beta 2, 790 bar; for alpha 2 holo beta 2, 1057 bar). Sucrose (13%) shifts both midpoints of transition to values higher by about 300 bar. As shown by sucrose gradient centrifugation and limited trypsinolysis, deactivation of the beta 2-dimer is paralleled by dissociation into denatured beta-chains. At 10 degrees C, the corresponding dissociation constants K at 1 bar as well as the reaction volumes of dissociation delta V are calculated as 4.2 x 10(-9) M and -196 mL/mol for the apo-beta 2-component and as 9.8 x 10(-19) M and -632 mL/mol for the holo-beta 2-component in the bienzyme complex. Furthermore, large negative activation volumes are determined, reflecting the rate increase with increasing pressure: -89 mL/mol for the apo-beta 2-dimer and -195 mL/mol for the holo-beta 2-dimer.(ABSTRACT TRUNCATED AT 250 WORDS)
机译：在高达2 kbar的静水压力下，由于比活性以及紫外线吸收和荧光发射光谱，从大肠杆菌中分离出的色氨酸合酶的α-亚基被证明是稳定的酶。因此，该蛋白可以被认为是研究在高静水压力下二聚体β2-亚基中结构-功能关系的合适效应子。高于1300 bar（alpha apo beta 2 2，790 bar;α2 holo beta 2，1057 bar）的转变中点会发生alpha 2 beta 2双酶复合物中β2组分的完全失活。蔗糖（13％）将过渡的两个中点都移至约300 bar的较高值。如蔗糖梯度离心和有限的胰蛋白酶消化所显示，β2-二聚体的失活与解离成变性的β-链平行。在10摄氏度下，相应的1 bar的解离常数K以及解离δV的反应体积计算为4.2 x 10（-9）M和-196 mL / mol（对于apo-beta 2组分而言），以及9.8 x 10（-19）M和-632 mL / mol的双酶复合物中的完整β2组分。此外，确定了较大的负激活体积，反映出速率随压力增加而增加：apo-beta 2-二聚体为-89 mL / mol，而holo-beta 2-dimer为-195 mL / mol。（摘要于250话）

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