What is the Active Species of Cytochrome P450 during Camphor Hydroxylation? QM/MM Studies of Different Electronic States of Compound I and of Reduced and Oxidized Iron−Oxo Intermediates

2007 ◽  
Vol 129 (29) ◽  
pp. 8978-8987 ◽  
Author(s):  
Ahmet Altun ◽  
Sason Shaik ◽  
Walter Thiel
Keyword(s):  
Cytochrome P450 ◽  
Electronic States ◽  
Active Species ◽  
Compound I ◽  
Oxidized Iron

scholarly journals Mechanism of 17α,20-Lyase and New Hydroxylation Reactions of Human Cytochrome P450 17A1

2016 ◽  
Vol 291 (33) ◽  
pp. 17143-17164 ◽  
Author(s):  
Francis K. Yoshimoto ◽  
Eric Gonzalez ◽  
Richard J. Auchus ◽  
F. Peter Guengerich
Keyword(s):  
Acetic Acid ◽  
Cytochrome P450 ◽  
Bond Cleavage ◽  
Active Species ◽  
Sterol Biosynthesis ◽  
Compound I ◽  
Human Cytochrome ◽  
Acetyl Radical

Cytochrome P450 (P450) reactions can involve C–C bond cleavage, and several of these are critical in steroid and sterol biosynthesis. The mechanisms of P450s 11A1, 17A1, 19A1, and 51A1 have been controversial, in the context of the role of ferric peroxide (FeO2−) versus perferryl (FeO3+, compound I) chemistry. We reinvestigated the 17α-hydroxyprogesterone and 17α-hydroxypregnenolone 17α,20-lyase reactions of human P450 17A1 and found incorporation of one 18O atom (from 18O2) into acetic acid, consonant with proposals for a ferric peroxide mechanism (Akhtar, M., Lee-Robichaud, P., Akhtar, M. E., and Wright, J. N. (1997) J. Steroid Biochem. Mol. Biol. 61, 127–132; Akhtar, M., Wright, J. N., and Lee-Robichaud, P. (2011) J. Steroid Biochem. Mol. Biol. 125, 2–12). However, the reactions were supported by iodosylbenzene (a precursor of the FeO3+ species) but not by H2O2. We propose three mechanisms that can involve the FeO3+ entity and that explain the 18O label in the acetic acid, two involving the intermediacy of an acetyl radical and one a steroid 17,20-dioxetane. P450 17A1 was found to perform 16-hydroxylation reactions on its 17α-hydroxylated products to yield 16,17α-dihydroxypregnenolone and progesterone, suggesting the presence of an active perferryloxo active species of P450 17A1 when its lyase substrate is bound. The 6β-hydroxylation of 16α,17α-dihydroxyprogesterone and the oxidation of both 16α,17α-dihydroxyprogesterone and 16α,17α-dihydroxypregnenolone to 16-hydroxy lyase products were also observed. We provide evidence for the contribution of a compound I mechanism, although contribution of a ferric peroxide pathway in the 17α,20-lyase reaction cannot be excluded.

Computational Study on Compound I Redox-Active Species in Horseradish Peroxydase Enzyme: Conformational Fluctuations and Solvation Effects

2010 ◽  
Vol 114 (20) ◽  
pp. 6817-6824 ◽  
Author(s):  
Costantino Zazza ◽  
Amedeo Palma ◽  
Nico Sanna ◽  
Simone Tatoli ◽  
Massimiliano Aschi
Keyword(s):  
Computational Study ◽  
Active Species ◽  
Compound I ◽  
Solvation Effects ◽  
Redox Active

New Features in the Catalytic Cycle of Cytochrome P450 during the Formation of Compound I from Compound 0

2005 ◽  
Vol 109 (42) ◽  
pp. 19946-19951 ◽  
Author(s):  
Devesh Kumar ◽  
Hajime Hirao ◽  
Sam P. de Visser ◽  
Jingjing Zheng ◽  
Dongqi Wang ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Catalytic Cycle ◽  
Compound I

Excited electronic states in dark biological process

1973 ◽  
Vol 6 (4) ◽  
pp. 485-501 ◽  
Author(s):  
G. Cilento
Keyword(s):  
Amino Acids ◽  
Excited States ◽  
Electronic Excitation ◽  
Light Emission ◽  
Biological Process ◽  
Electronic States ◽  
Aromatic Amino Acids ◽  
Active Species ◽  
Excited Electronic States ◽  
Transfer Processes

It is well known that excited states may be generated chemically in biological systems as evidencex and by the phenomenon of bioluminescence and it is natural to suspect that they may also be generated and used in dark processes (Szent-Györgyi, 1941; Steele, 1963; Cilento, 1965; White & Wei, 1970; Whiteet al.1971). Förster (1967) has pointed out that electronic excitation and subsequent transfer processes may occur in biological dark systems despite the fact that the energy available from enzymic processes is too low to excite aromatic amino acids and other biochemical structures. Hastings (1968) suggests that in some organisms light emission is just an alternative to the formation of an active species.

scholarly journals A DFT Study of the Heme Role in the N-Demethylation of Theophylline Mediated by Compound I of Cytochrome P450

2007 ◽  
Vol 48 (4) ◽  
pp. 730-734 ◽  
Author(s):  
Mohamed Ismael ◽  
Carlos A. Del Carpio ◽  
Abdul Rajjak Shaikh ◽  
Hideyuki Tsuboi ◽  
Michihisa Koyama ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Dft Study ◽  
Compound I
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