Electron paramagnetic resonance detection of intermediates in the enzymatic cycle of an extradiol dioxygenase.
Extradiol catecholic dioxygenases catalyze the cleavage of the aromatic ring of the substrate with incorporation of both oxygen atoms from O2. These enzymes are important in nature for the recovery of large amounts of carbon from aromatic compounds. The catalytic site contains either Fe or Mn coordinated by a facial triad of two His and one Glu or Asp residues. Previous studies have shown that Fe(II) and Mn(II) can be interchanged in enzymes from different organisms to catalyze similar substrate reactions. In combination, quantitative electron paramagnetic resonance spectroscopy and rapid freeze-quench experiments allow us to follow the concentrations of four different Mn species, including key metal intermediates in the catalytic cycle, as the enzyme turns over its natural substrate. Two intermediates are observed: a Mn(III)-radical species which is either Mn-superoxide or Mn-substrate radical, and a unique Mn(II) species which is involved in the rate-limiting step of the cycle and may be Mn-alkylperoxo.
Gunderson
William A
WA
Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Zatsman
Anna I
AI
Emerson
Joseph P
JP
Farquhar
Erik R
ER
Que
Lawrence
L
Lipscomb
John D
JD
Hendrich
Michael P
MP
D015102:3,4-Dihydroxyphenylacetic Acid / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D049308:Dioxygenases / Q000737:chemistry* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010105:Oxygenases / Q000737:chemistry* / Q000378:metabolism
D015102:3,4-Dihydroxyphenylacetic Acid; D008345:Manganese; D010105:Oxygenases; D049308:Dioxygenases; C020055:3,4-dihydroxyphenylacetate 2,3-dioxygenase; C439587:extradiol dioxygenase; D010100:Oxygen