Bryan J. Johnson, Jordi Cohen, Richard W. Welford, Arwen R. Pearson, Klaus
Schulten, Judith P. Klinman, and Carrie M. Wilmot.
Exploring molecular oxygen pathways in Hanseluna Polymorpha
copper-containing amine oxidase.
Journal of Biological Chemistry, 282:17767-17776, 2007.
(PMC: 3081669)
JOHN2007
The accessibility of large substrates to buried enzymatic active sites is dependent upon
the utilization of proteinaceous channels. The necessity of these channels in the case of
small substrates is questionable as diffusion through the protein matrix is often assumed.
Copper amine oxidases (CAOs) contain a buried protein-derived quinone cofactor and a
mononuclear copper center that catalyze the conversion of two substrates, primary amines
and molecular oxygen, to aldehydes and hydrogen peroxide respectively. The nature of
molecular oxygen migration to the active site in the enzyme from Hansenula
polymorpha (HPAO) is explored using a combination of kinetic, X-ray crystallographic and
computational approaches. A crystal structure of HPAO in complex with xenon gas, which
serves as an experimental probe for molecular oxygen binding sites, reveals buried
regions of the enzyme suitable for transient molecular oxygen occupation. The calculation
of O free energy maps corresponds well with the xenon binding sites, and helps
connect individual sites into routes with differing probabilities. Site-directed mutagenesis
designed to block individual routes has little effect on overall /[O],
supporting multiple dynamic pathways for molecular oxygen to reach the active site.
free energy maps corresponds well with the xenon binding sites, and helps
connect individual sites into routes with differing probabilities. Site-directed mutagenesis
designed to block individual routes has little effect on overall 
/
[O
