BIOINORGANIC CHEMISTRY A Short Course Second Edition

440 IRON-CONTAINING PROTEINS AND ENZYMES

7.8.4 Cytochrome c Oxidase Model Compounds and Associated
Analytical Techniques

In 2004, Kenneth Karlin and co - workers published an extensive review of
cytochrome c oxidase model compounds.^138 Hundreds of CcO models exist,
with more being synthesized and studied into the current time. These can be
broken down into a number of categories as Karlin ’ s group does in the 2004

Figure 7.42 The cytochrome c oxidase reaction cycle starting from the fully reduced
state.

A

F

R

fully reduced state

CuAI-CuAI

heme a FeII

8-10μs O 2 binding

CuAI-CuAI

heme a FeII

30-50μs

O-O bond cleavage

formation oxo-ferryl state at heme a 3

eT from heme a to CuB-heme a 3 catalytic site

internal pT at catalytic site (possible H transfer

from YOH to CuB(I))

CuAI-CuAI

heme a FeIII

100-120μs

pT to a group at the catalytic site

(possibly to YO- or CuBII-OH)

pT from the bulk solution

eT from CuA to heme a

proton pumping

pT to heme a 3 oxo-ferryl group

formation of OH- group

pT from bulk solution

eT from CuA and heme a to catalytic site

proton pumping

O

fully oxidized state

1-3 ms

FeIII OH

heme a 3

FeII

heme a 3

heme a 3

FeII O

O

YO-

HO CuBII

heme a 3

FeIVO2-

FeIVO2-

YO- HO-CuBII and YOH also

possible

CuBI

YOH

CuBI

H 2 O CuBII

HO CuBII

YO-

CuAI-CuAII

heme a FeII

CuAI-CuAI

heme a FeIII

heme a 3

CuAI-CuAII

heme a FeIII

ν(Fe-OH) = 450 cm-1

λ = ~580 nm

ν(FeIV=O) = 785 cm-1

λ = ~595 nm

ν(FeII- O) = 571 cm-1

or YO

.

as in PM

or H 2 O-CuBII

2H+, 2 e-

proton pumping

YOH or FeIII-O 2 - (superoxo)

PR

2 H 2 O