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Pure Appl. Chem.
76(2), 303-319, 2004
Pure and Applied
Vol. 76, Issue 2
Understanding the reaction that powers this world: Biomimetic studies
of respiratory O2 reduction by cytochrome oxidase
Department of Chemistry and Chemical Biology, Harvard
University, Cambridge, MA 02138, USA
Abstract: Cytochrome c oxidase (CcO) is an enzyme that
catalyzes efficient, selective, and fast reduction of molecular oxygen
to water as a means of respiratory energy generation. The biomimetic
approach provides a valuable alternative to traditional biochemical
methods to unravel the structural and electronic properties of the CcO's
catalytic (heme/CuB) site that endow the enzyme with its
unique reactivity. However, the contribution of biomimetic studies of
CcO to our understanding of CcO's biochemistry has been complicated
by the lack of convincing evidence that the reactivity of the biomimetic
analogs is relevant to that of CcO. Recently reported porphyrin-based
compounds are the first analogs that reproduce key aspects of the reactivity
of CcO toward O2. Extensive data collected with these biomimetic
analogs demonstrate that the bimetallic nature of the CcO's catalytic
site may be an adaptation to reduction of O2 under turnover-limiting
electron flux; a monometallic heme-only site appears sufficient for
rapid O2 reduction under physiologically relevant conditions
of pH and electrochemical potential, provided that electron flow to
the heme is not kinetically limited. These biomimetic data suggest that
in CcO the distal Cu ion (CuB) may serve as an electron-preloading
site to allow the enzyme to accumulate a sufficient number of external
reducing equivalents before it even binds O2. This mechanism
minimizes the population of enzymatic species containing partially reduced
[full text - pdf 502KB]
+ Erratum Pure Appl. Chem.
76(6), 1293, 2004
*Pure Appl. Chem. 76,
263-319 (2004). A collection of invited, peer-reviewed articles
by the winners of the 2003 IUPAC Prize for Young Chemists.
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