کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9882150 | 1536542 | 2005 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Reduction of cytochrome b5 by NADPH-cytochrome P450 reductase
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کلمات کلیدی
موضوعات مرتبط
علوم زیستی و بیوفناوری
بیوشیمی، ژنتیک و زیست شناسی مولکولی
زیست شیمی
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چکیده انگلیسی
The reduction of mammalian cytochrome b5 (b5) by NADPH-cytochrome P450 (P450) reductase is involved in a number of biological reactions. The kinetics of the process have received limited consideration previously, and a combination of pre-steady-state (stopped-flow) and steady-state approaches was used to investigate the mechanism of b5 reduction. In the absence of detergent or lipid, a reductase-b5 complex is formed and rearranges slowly to an active form. Electron transfer to b5 is rapid within this complex (>30 sâ1 at 23 °C), as fast as to cytochrome c. With excess b5 present, a burst of reduction is observed, consistent with rapid electron transfer to one or two b5 molecules per reductase, followed by a subsequent rate-limiting event. In detergent vesicles, the reductase and b5 interact rapidly but electron transfer is slower (â¼3 sâ1 at 23 °C). Experiments with dimyristyl lecithin vesicles yielded results intermediate between the non-vesicle and detergent systems. These steady-state and pre-steady-state kinetics provide views of the different natures of the reduction of b5 by the reductase in the absence and presence of vesicles. Without vesicles, the encounter of the reductase and b5 is rapid, followed by a slow reorganization of the initial complex (â¼0.07 sâ1), very fast reduction, and dissociation. In vesicles, encounter is rapid and the slow step (â¼3 sâ1) is reduction within a complex less favorable for reduction than in the non-vesicle systems.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 440, Issue 2, 15 August 2005, Pages 204-211
Journal: Archives of Biochemistry and Biophysics - Volume 440, Issue 2, 15 August 2005, Pages 204-211
نویسندگان
F. Peter Guengerich,