Search this Site

Print this page
RSS

Department of Biochemistry, Molecular Biology and Biophysics, BMBB, University of Minnesota

"Visualizing the Steps in Oxygen Activation by Fe(II) Dioxygenases"

Prof. John Lipscomb

Monday May 02, 2011

3:30pm PHYS 203

Unless otherwise noted, seminars are held on Mondays at 3:30 p.m. in Physics Room 203. Coffee served at 3:15pm in Phys 244.

http://www.cbs.umn.edu/BMBB/html/Faculty/Lipscomb.J.D.html

Aromatic ring cleaving dioxygenases catalyze the critical step in the biodegradation of the nearly unimaginable quantities of aromatic compounds produced annually by plants and through man’s activities in agriculture and industry. One common type of enzyme from this family utilizes a single Fe(II) in the active site and cleaves the aromatic ring of catechols at a position adjacent to the diol function. We have used these extradiol dioxygenases principally to explore their mechanism of O2 activation. However, they have also proven useful in the development of new methods to explore enzyme catalysis in general. Methods to detect and trap intermediates in the oxygen activation and insertion reactions carried out in solution and in single crystals will be discussed. The studies have resulted in the first structurally and spectroscopically characterized intermediates in this enzyme family. The intermediates support a novel mechanism in which simultaneous binding to the Fe(II) of the catechol and O2 substrates allows electron transfer from the former to the latter. This yields two radicals in close proximity that recombine to initiate catalysis and overcome the triplet problem inherent in all oxygenase reaction mechanisms.