ANALYSIS OF THE PH- AND LIGAND-INDUCED SPECTRAL TRANSITIONS OF TRYPTOPHANASE : ACTIVATION OF THE COENZYME AT THE EARLY STEPS OF THE CATALYTIC CYCLE
ANALYSIS OF THE PH- AND LIGAND-INDUCED SPECTRAL TRANSITIONS OF TRYPTOPHANASE : ACTIVATION OF THE COENZYME AT THE EARLY STEPS OF THE CATALYTIC CYCLE
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色氨酸酶 PH 值和配体诱导的光谱跃迁分析：催化周期早期辅酶的激活
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
H. Kagamiyama
中科院分区：
文献类型：
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作者：
H. Ikushiro;H. Hayashi;Y. Kawata;H. Kagamiyama
色氨酸酶在高pH时的最大吸收波长为338 nm，在低pH时为422 nm。422 nm的吸收物种被认为是5‘-磷酸吡哆醛席夫碱的催化活性酮烯胺形式，带有赖氨酸残基。338 nm吸收峰在390 nm处有一个较强的荧光带，而不是在500 nm附近，这表明338 nm吸收峰是取代的阿尔丹明，而不是先前提出的席夫碱的烯醇亚胺形式。研究了色氨酸酶与底物类似物3-吲哚丙酸在不同pH值和不同类似物浓度下的反应，以探讨该酶在高pH条件下发挥催化作用的机理。动力学分析是基于一个方案，涉及8种形式的酶，即连接形式和非连接形式的酮胺...
Tryptophanase has an absorption maximum at 338 nm at high pH and 422 nm at low pH. The 422-nm absorption species has been considered to be the catalytically competent ketoenamine form of the Schiff base of pyridoxal 5‘-phosphate with a lysine residue. The 338-nm absorption band showed an intense fluorescence band at 390 nm and not around 500 nm, indicating that the 338-nm absorption species is the substituted aldamine rather than an enolimine form of the Schiff base which has been suggested previously. To explore the mechanism of the enzyme that can exert its catalytic ability at high pH where most of its coenzyme exists as the catalytically incompetent aldamine structure, the reaction of tryptophanase with 3-indolepropionate, a substrate analogue that stops the reaction at the step of the Michaelis complex, was studied at various pH values and analogue concentrations. Kinetic analysis was done based on a scheme involving eight forms of the enzyme, i.e., the liganded and unliganded forms of the ketoenamin...