TAILIEUCHUNG - Báo cáo khoa học: Interflavin electron transfer in human cytochrome P450 reductase is enhanced by coenzyme binding

The role of coenzyme binding in regulating interflavin electron transfer in human cytochrome P450 reductase (CPR) has been studied using temperature-jump spectros-copy. Previous studies [Gutierrez, A., Paine, M., Wolf, ., Scrutton, ., & Roberts, (2002) 41,4626–4637] have shown that the observed rate, 1/s, of interflavin electron transfer (FADsq )FMNsq fi FADox)FMNhq) inCPRreduced at the two-electron level with NADPH is 55 ± 2 s )1 , whereas with dithionite-reduced enzyme the observed rate is 11 ± s )1 ,sug-gesting that NADPH (or NADP + ) binding has an important role in controlling the rate of internal electron transfer | Eur. J. Biochem. 270 2612-2621 2003 FEBS 2003 doi Interflavin electron transfer in human cytochrome P450 reductase is enhanced by coenzyme binding Relaxation kinetic studies with coenzyme analogues Aldo Gutierrez1 2 Andrew W. Munro1 Alex Grunau1 2 C. Roland Wolf3 Nigel S. Scrutton1 and Gordon C. K. Roberts1 2 1 Department of Biochemistry and 2Biological NMR Centre University of Leicester UK 3Biomedical Research Centre University of Dundee Ninewells Hospital and Medical School Dundee UK The role of coenzyme binding in regulating interflavin electron transfer in human cytochrome P450 reductase CPR has been studied using temperature-jump spectroscopy. Previous studies Gutierrez A. Paine M. Wolf . Scrutton . Roberts . Biochemistry 2002 41 4626-4637 have shown that the observed rate 1 s of interflavin electron transfer FADsq - FMNsq fi FADox - FMNhq in CPR reduced at the two-electron level with NADPH is 55 2 s-1 whereas with dithionite-reduced enzyme the observed rate is 11 s-1 suggesting that NADPH or NADP binding has an important role in controlling the rate of internal electron transfer. In relaxation experiments performed with CPR reduced at the two-electron level with NADH the observed rate of internal electron transfer 1 s 18 s-1 is intermediate in value between those seen with dithionite-reduced and NADPH-reduced enzyme indicating that the presence of the 2 -phosphate is important for enhancing internal electron transfer. To investigate this further temperature jump experiments were performed with dithionite-reduced enzyme in the presence of 2 5 -ADP and 2 -AMP. These two ligands increase the observed rate of interflavin electron transfer in two-electron reduced CPRfrom 1 s 11 s-1to35 s-1 and 32 s-1 respectively. Reduction of CPR at the two-electron level by NADPH NADH or dithionite generates the same spectral species consistent with an electron distribution that is equivalent regardless of reductant at

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