Spectroscopic features of cytochrome P450 reaction intermediates

• Published in: Archives of biochemistry and biophysics 2011-03, Vol.507 (1), p.26-35
• Main Authors: Luthra, Abhinav, Denisov, Ilia G., Sligar, Stephen G.
• Format: Article
• Language: English
• Subjects: absorption; Animals; Circular Dichroism - methods; cytochrome P-450; Cytochrome P-450 Enzyme System - chemistry; Cytochrome P-450 Enzyme System - metabolism; Cytochrome P450; Electron Spin Resonance Spectroscopy - methods; heme; Heme - chemistry; Heme - metabolism; heme iron; hemoglobin; Humans; hydroxylation; isozymes; Metalloenzyme mechanisms; monitoring; myoglobin; nitric oxide synthase; Nuclear Magnetic Resonance, Biomolecular - methods; organisms; spectral analysis; Spectrophotometry - methods; Spectroscopy; Spectroscopy, Mossbauer - methods; Spectrum Analysis - methods; Spectrum Analysis, Raman - methods; X-Ray Absorption Spectroscopy - methods
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2010.12.008

► Cytochromes P450 provide a rich landscape of spectroscopic features. ► Advantages of various spectroscopic methods for P450 studies are compared. ► Signature spectroscopic markers of P450 intermediates are summarized. ► Spectroscopy is indispensable for mechanistic characterization of P450 catalysis. Cytochromes P450 constitute a broad class of heme monooxygenase enzymes with more than 11,500 isozymes which have been identified in organisms from all biological kingdoms [1]. These enzymes are responsible for catalyzing dozens chemical oxidative transformations such as hydroxylation, epoxidation, N-demethylation, etc., with very broad range of substrates [2,3]. Historically these enzymes received their name from ‘pigment 450’ due to the unusual position of the Soret band in UV–vis absorption spectra of the reduced CO-saturated state [4,5]. Despite detailed biochemical characterization of many isozymes, as well as later discoveries of other ‘P450-like heme enzymes’ such as nitric oxide synthase and chloroperoxidase, the phenomenological term ‘cytochrome P450’ is still commonly used as indicating an essential spectroscopic feature of the functionally active protein which is now known to be due to the presence of a thiolate ligand to the heme iron [6]. Heme proteins with an imidazole ligand such as myoglobin and hemoglobin as well as an inactive form of P450 are characterized by Soret maxima at 420 nm [7]. This historical perspective highlights the importance of spectroscopic methods for biochemical studies in general, and especially for heme enzymes, where the presence of the heme iron and porphyrin macrocycle provides rich variety of specific spectroscopic markers available for monitoring chemical transformations and transitions between active intermediates of catalytic cycle.