Galactose oxidase (GOase) catalyzes the oxidation of primary alcohols to aldehydes using molecular oxygen.  GOase has two one-electron redox centers at the active site, a tyrosine radical/tyrosinate and a mononuclear Cu(II)/Cu(I).
This seminar will summarize our work over the past several years on the radical mechanism of galactose oxidase. It will cover several aspects of radical redox catalysis by galactose oxidase (GOase).
The use of radical-probing substrates to study GOase reaction mechanisms will be described.  Special features of the active site which enhance catalysis by a radical mechanism will be described in the context of a semi-quantitative energy profile that we have constructed for the energetics of the GOase catalytic cycle.  From our studies and those of others, a clear picture emerges of how GOase can catalyze one-electron redox processes such as H-atom transfers and electron transfers.

"Preparation of Fully Oxidized Active and Reduced Inactive Forms of Galactose Oxidase from Dactylium dendroides Using Ferricyanide-Containing Oxidizing and Ferrocyanide-Containing Reducing Forms of Ion Exchange Resins", Montague-Smith, M. P.; Wachter, R. M.; Branchaud, B. P. Analytical Biochemistry 1992, 207, 353-355."Mechanism-Based Inactivation of Galactose Oxidase:  Evidence for a Radical Mechanism", Branchaud, B. P.; Montague-Smith, M. P.; Kosman, D. J.; McLaren, F. R.  The Journal of the American Chemical Society  1993, 115, 798-800.
"Molecular Modeling Studies on Oxidation of Hexopyranoses by Galactose Oxidase.  An Active Site Topology Apparently Designed To Catalyze Radical Reactions, Either Concerted or Stepwise", Wachter, R. M.; Branchaud B. P. The Journal of the American Chemical Society  1996, 118, 2782-2789.
"Thiols as Mechanistic Probes for Catalysis by the Free Radical Enzyme Galactose Oxidase", Wachter, R. M.; Branchaud, B. P. "Biochemistry. 1996, 35, 14425-14435.
"beta-Haloethanol Substrates As Probes For Radical Mechanisms For Galactose Oxidase", Wachter, R. M.; Montague-Smith, M.; Branchaud, B. P.  The Journal of the American Chemical Society  1997, 119, 7743-7749.
"Construction and Analysis of a Semi-Quantitative Energy Profile for the Reaction Catalyzed by the Radical Enzyme Galactose Oxidase", Wachter, R. M.; Branchaud, B. P. Biochimica et Biophysica Acta 1998 1384, 43-54.
"Probing the Radical Mechanism of Galactose Oxidase Using An Ultrafast Radical Probe", Turner, B. E.; Branchaud, B. P., Bioorganic & Medicinal Chemistry Letters 1999, 9, 3341-5.
"Galactose Oxidase: Probing the Radical Mechanism with an Ultrafast Radical Probe", Branchaud, B. P. Invited Chapter In Methods in Enzymology, Enzyme Kinetics and Mechanisms Part F, Detection and Characterization of Enzyme Reaction Intermediates, 2002, in press.
 

Last modified 30 August 2002