Chemistry Reference
In-Depth Information
(a)
(b)
FIGURE 13.11
(a) High-resolution structure of cytochrome P450 from Pseudomonas putida displaying a water channel above the haem.
(Adapted with permission from Poulos et al., 1986, Copyright (1986) American Chemical Society). (b) The peroxo-shunt mechanism of mono-
oxygenases produces compound I (P
þ
Fe
IV
]
O), which oxidizes substrates by their nucleophilic attack on the electrophilic oxo of the (P
þ
)
Fe
IV
]
O core.
(Reproduced with permission from
Dempsey, Esswein, Manke, et al., 2005
, Copyright (2005) American Chemical Society.)
FIGURE 13.12
Catalytic cycle of cytochrome P450. The cytochrome P450 catalytic cycle with the compound I-like ferryl species high-
lighted by a blue square. The haem is represented by the iron between two bars, which stand for the porphyrin framework. RH is a hydrocarbon
substrate and ROH its alcohol product.
(From
Johnston et al., 2011
.
Copyright 2011, with permission from Elsevier.)
atom in this ferryl species is paired with a radical cation delocalized over the haem porphyrin ring, so the enzyme
is two oxidation equivalents higher than the resting enzyme.
Electron Transport Proteins
The third class of hemoproteins are the cytochromes. They were first discovered by C.A. McMunn, a rural physician
in Wolverhampton, who identified their characteristic absorption bands, and by manipulating their oxidation and
