NADPH cytochrome P450 reductase

The microsomal fraction consists mainly of vesicles (microsomes) derived from the endoplasmic reticulum (smooth and rough). It contains cytochrome P450 and NADPH/cytochrome P450 reductase (collectively the microsomal monooxygenase system), carboxylesterases, A-esterases, epoxide hydrolases, glucuronyl transferases, and other enzymes that metabolize xenobiotics. The 105,000 g supernatant contains soluble enzymes such as glutathione-5-trans-ferases, sulfotransferases, and certain esterases. The 11,000 g supernatant contains all of the types of enzyme listed earlier. 

Cytochrome P450s catalyze reactions that introduce one atom of oxygen derived from molecular oxygen into the substrate, yielding a hydroxylated product. NADPH and NADPH-cytochrome P450 reductase are involved in the complex reaction mechanism. 

Yamazaki, H., Ueng, Y.F., Shimada, T. and Guengerich, F.P. (1995) Roles of divalent metal ions in oxidations catalyzed by recombinant cytochrome P450 3A4 and replacement of NADPH-cytochrome P450 reductase with other flavoproteins, ferredoxin, and oxygen surrogates. Biochemistry, 34, 8380—8389. 

E. G., Creation of polarized cells coexpressing CYP3A4, NADPH cytochrome P450 reductase and MDRl/P-glycoprotein, Pharm. Res. 2000, 37, 803-810. 

NAD PI I gives up hydrogen atoms to the flavo protein NADPH— cytochrome P450 reductase and becomes NADP+. The reduced flavo protein transfers these reducing equivalents to cytochrome P450. The reducing... 

URBAN, P., MIGNOTTE, C., KAZMAIER, M., DELORME, F., POMPON, D., Cloning, yeast expression, and characterization of the coupling of two distantly related Arabidopsis thaliana NADPH-cytochrome P450 reductases with P450 CYP73A5, Bio. Chem., 1997,272, 19176-86. 

McGuire, J., Anderson, D. J., MacDonald, B. J., Narayanasami, R., Bennett, B. M., Inhibition of NADPH-cytochrome P450 reductase and glyceryl trinitrate biotransformation by diphenyleneiodonium sulfate. 

Guengerich, F.P. (2005) Reduction of cytochrome b5 by NADPH-cytochrome P450 reductase. Archives of Biochemistry and Biophysics, 440 (2), 204-211. 

NADPH-cytochrome P450 reductase was purified from rat brain microsomes. 

High NADPH cytochrome P450 reductase activity is found in immature rat brain and neuronal cultures, but very little cytochrome P450, thus NADPH cytochrome P450 reductase may be involved in cytochrome P450 independent pathways (Ghersi-Egea et al., 1993). 

Eight human brain tumors contained DT-diaphorase, NADH cytochrome b5 reductase and NADPH cytochrome P450 reductase as assessed by enzyme activity and WB (Rampling et al., 1994). 

Bergh AF, Strobel HW. 1992. Reconstitution ofthe brain mixed function oxidase system purification of NADPH-cytochrome P450 reductase and partial purification of cytochrome P450 from whole rat brain. J Neurochem 59 575-581. 

Bergh AF, Strobel HW. 1996. Anatomical distribution of NADPH-cytochrome P450 reductase and cytochrome P4502D forms in rat brain effects of xenobiotics and sex steroids. Mol Cell Biochem 162 31-41. 

Haglund L, Kohler C, Haaparanta T, Goldstein M, Gustafsson JA. 1984. Presence of NADPH-cytochrome P450 reductase in central catecholaminergic neurones. Nature 307 ... 

Pappolla MA, Omar RA, Chyan YJ, Ghiso J, Hsiao K, et al. 2001. Induction of NADPH cytochrome P450 reductase by the Alzheimer beta-protein. Amyloid as a foreign body. J Neurochem 78 121-128. 

Cinnamate 4-hydroxylase (C4H EC 1.14.13.11, also defined as CYP73A [36]) catalyzes the p-hydroxylation of trani-cinnamate to form trani -p-coumarate. The enzyme has a requirement for molecular oxygen and NADPH as well as association with the electron donor NADPH-cytochrome P450 reductase (CPR EC 1.6.2.4) for activity. C4H was the first characterized plant P450 [37, 38]. 

A single turnover study of the conversion of the heme-HO-1 complex to free biliverdin has elucidated the relative rates of the catalytic steps 129). This transient kinetic study indicates that the conversion of Fe heme to Fe verdoheme is biphasic. Electron transfer to the Fe -heme HO-1 complex occurred at a rate of 0.11 s at 4°C and 0.49 s at 25°C with a 0.1 1 ratio of NADPH-cytochrome P450 reductase to heme HO-l complex. Oxygen binding to the reduced iron was sufficiently rapid im-der the experimental conditions that the species actually monitored... 

However, in contrast to the human His25Ala HO-l heme complex, which has no detectable activity in the absence of imidazole (78), the His20Ala Hmu O rheme complex in the presence of NAD PH and NADPH-cytochrome P450 reductase was foimd to catalyze the initial meso-hydroxylation of the heme (151). The product of the reaction was Fe verdoheme, as judged by the electronic absorption spectrum and the detection of carbon monoxide as a product of the reaction. Hydrolytic conversion of the verdoheme product to biliverdin and subsequent HPLC analysis confirmed that the oxidative cleavage of the porphyrin macrocycle was specific for the a-meso-carbon. 

Modi, S., Gilham, D. E., Sutcliffe, M. J., et al. (1997) l-Methyl-4-pheny 1-1,2,3,6-tetrahydropyridine as a substrate of cytochrome P450 2D6 allosteric effects of NADPH-cytochrome P450 reductase. Biochemistry 36, 4461-4470. 

Cawley, G.F., Bade, C.J. and Backes, W.L. (1995) Substrate-dependent competition of different P450 isozymes for limiting NADPH-cytochrome P450 reductase. Biochemistry, 34, 1244—1247. 

Evaluation of approach to predict the contribution of multiple cytochrome P450s in drug metabolism using relative activity factor effects of the differences in expression levels of NADPH-cytochrome P450 reductase and cytochrome b(5) in the expression system and the differences in the marker activities. Journal of Pharmaceutical Sciences, 91, 952—963. 

NADPH)-cytochrome P450 reductase. The other is P450arom. a hemoprotein of 530 amino acids with a molecular weight of ca. 55 kDa. 

The answers are 34-g, 33-a, 36-d. (Katzung, pp 53-56.) There are four major components to the mixed-function oxidase system (1) cytochrome P450, (2) NADPH, or reduced nicotinamide adenine dinucleotide phosphate, (3) NADPH-cytochrome P450 reductase, and (4) molecular oxygen. The figure that follows shows the catalytic cycle for the reactions dependent upon cytochrome P450. 

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