脊索变位酶
枯草芽孢杆菌
化学
酶
变位酶
立体化学
碳-13核磁共振
生物化学
细菌
生物
生物合成
遗传学
作者
Joseph V. Gray,Devrim Eren,Jeremy R. Knowles
出处
期刊:Biochemistry
[American Chemical Society]
日期:1990-09-18
卷期号:29 (37): 8872-8878
被引量:57
摘要
The interaction of the monofunctional chorismate mutase from Bacillus subtilis with chorismate and prephenate has been studied kinetically and by NMR spectroscopy with 13C specifically labeled substrates. Prephenate dominates the population of enzyme-bound species, and the "off" rate constant (approximately 60 s-1) obtained from line-broadening experiments is close to the value of kcat for chorismate (50 s-1) determined kinetically. The calculated "on" rate constant for prephenate (8 x 10(5) M-1 s-1) is similar to the value of kcat/Km for chorismate (5 x 10(5) M-1 s-1). The kinetic parameters of the Bacillus mutase are remarkably insensitive to pH over a wide range and display no solvent isotope effect. These results suggest that the enzyme-catalyzed reaction may be encounter controlled (slowed from the diffusion limit by some feature of the enzyme's active site) and that kcat for chorismate is determined by the product off rate. There is now no evidence to suggest that the skeletal rearrangement on the enzyme surface occurs by a pathway other than a pericyclic process.
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