CHANGES IN THE FLUORESCENCE OF BOUND NUCLEOTIDE DURING THE REACTION CATALYZED BY GLUCOSE-FRUCTOSE OXIDOREDUCTASE FROM ZYMOMONAS-MOBILIS

被引:10
作者
HARDMAN, MJ [1 ]
TSAO, M [1 ]
SCOPES, RK [1 ]
机构
[1] LA TROBE UNIV,DEPT BIOCHEM,BUNDOORA,VIC 3083,AUSTRALIA
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1992年 / 205卷 / 02期
关键词
D O I
10.1111/j.1432-1033.1992.tb16834.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The reduction of gluconolactone by glucose-fructose oxidoreductase containing tightly bound NADPH (enzyme-NADPH) is biphasic in nucleotide fluorescence. The initial rapid decrease, which represents quenching of the fluorescence by bound lactone, is followed by a slower decrease which corresponds to the change in absorbance. At low glucose concentrations, the oxidation of glucose by enzyme-NADP+ involves a single first-order process with similar rate constants in fluorescence and absorbance. At higher glucose concentrations, the apparent first-order rate constants for the fluorescence change are less than those for the absorbance change. This is consistent with a mechanism in which the fluorescence change occurs during the lactone dissociation step, which is slower than the hydrogen transfer step during which the absorbance change occurs. The rate constant for gluconolactone dissociation is 360 +/- 10 s-1 and this step is therefore rate-determining for the overall reaction. Reduction of fructose by enzyme-NADPH is first order with a limiting rate constant of at least 2000 s-1.
引用
收藏
页码:715 / 720
页数:6
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