动力学特性4-amino 4-deoxychorismate合酶大肠杆菌。
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Viswanathan VK、绿色JM,尼科尔斯BP
动力学特性4-amino 4-deoxychorismate合酶大肠杆菌。
J Bacteriol。1995年10月,177(20):5918 - 23所示。
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7592344 (在PubMed]
- 文摘
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代谢的命运p-aminobenzoic酸(PABA)在大肠杆菌是其并入维生素叶酸。PABA来源于芳香分枝点前体chorismate在两个步骤。Aminodeoxychorismate (ADC)合酶转换chorismate谷氨酸和谷氨酰胺ADC和由两个亚基组成,PabA PabB。从ADC ADC裂合酶除去丙酮酸,使芳香环,生成PABA。虽然有很多感兴趣的机理chorismate氨基化,几乎没有工作在ADC合酶反应。我们报告PabA需要预孵化与二硫苏糖醇最大活动以支持能力glutamine-dependent PabB chorismate胺。PabB谷氨酰胺提高PabA的保护作用。孵化新的二硫苏糖醇逆转PabB的失活。我们得出这样的结论:PabA和PabB半胱氨酸残基都是至关重要的,为催化功能和/或亚基相互作用。使用条件建立了最大活性的蛋白质,我们测量的Km值glutamine-dependent和ammonia-dependent chorismate氨基化,催化单靠PabB和ADC合酶复杂。 Kinetic studies with substrates and the inhibitor 6-diazo-5-oxo-L-norleucine were consistent with an ordered bi-bi mechanism in which chorismate binds first. No inhibition of ADC synthase activity was observed when p-aminobenzoate, sulfanilamide, sulfathiazole, and several compounds requiring folate for their biosynthesis were used.