کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1939954 1050771 2006 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Quantum mechanical hydrogen tunneling in bacterial copper amine oxidase reaction
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
Quantum mechanical hydrogen tunneling in bacterial copper amine oxidase reaction
چکیده انگلیسی

A key step decisively affecting the catalytic efficiency of copper amine oxidase is stereospecific abstraction of substrate α-proton by a conserved Asp residue. We analyzed this step by pre-steady-state kinetics using a bacterial enzyme and stereospecifically deuterium-labeled substrates, 2-phenylethylamine and tyramine. A small and temperature-dependent kinetic isotope effect (KIE) was observed with 2-phenylethylamine, whereas a large and temperature-independent KIE was observed with tyramine in the α-proton abstraction step, showing that this step is driven by quantum mechanical hydrogen tunneling rather than the classical transition-state mechanism. Furthermore, an Arrhenius-type preexponential factor ratio approaching a transition-state value was obtained in the reaction of a mutant enzyme lacking the critical Asp. These results provide strong evidence for enzyme-enhanced hydrogen tunneling. X-ray crystallographic structures of the reaction intermediates revealed a small difference in the binding mode of distal parts of substrates, which would modulate hydrogen tunneling proceeding through either active or passive dynamics.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biochemical and Biophysical Research Communications - Volume 342, Issue 2, 7 April 2006, Pages 414–423
نویسندگان
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