Catecholase activity of a mu-hydroxodicopper(II) macrocyclic complex: structures, intermediates and reaction mechanism.
The monohydroxo-bridged dicopper(II) complex (1), its reduced dicopper(I) analogue (2) and the trans-mu-1,2-peroxo-dicopper(II) adduct (3) with the macrocyclic N-donor ligand [22]py4pz (9,22-bis(pyridin-2'-ylmethyl)-1,4,9,14,17,22,27,28,29,30- decaazapentacyclo -[22.2.1(14,7).1(11,14).1(17,20)]triacontane-5,7(28),11(29),12,18,20(30), 24(27),25-octaene), have been prepared and characterized, including a 3D structure of 1 and 2. These compounds represent models of the three states of the catechol oxidase active site: met, deoxy (reduced) and oxy. The dicopper(II) complex 1 catalyzes the oxidation of catechol model substrates in aerobic conditions, while in the absence of dioxygen a stoichiometric oxidation takes place, leading to the formation of quinone and the respective dicopper(I) complex. The catalytic reaction follows a Michaelis-Menten behavior. The dicopper(I) complex binds molecular dioxygen at low temperature, forming a trans-mu-1,2-peroxo-dicopper adduct, which was characterized by UV-Vis and resonance Raman spectroscopy and electrochemically. This peroxo complex stoichiometrically oxidizes a second molecule of catechol in the absence of dioxygen. A catalytic mechanism of catechol oxidation by 1 has been proposed, and its relevance to the mechanisms earlier proposed for the natural enzyme and other copper complexes is discussed.
Koval
Iryna A
IA
Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300, RA, Leiden, Netherlands.
Belle
Catherine
C
Selmeczi
Katalin
K
Philouze
Christian
C
Saint-Aman
Eric
E
Schuitema
Anna Maria
AM
Gamez
Patrick
P
Pierre
Jean-Louis
JL
Reedijk
Jan
J
D002384:Catalysis; D002396:Catechols / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
D002396:Catechols; D007202:Indicators and Reagents; D009942:Organometallic Compounds; D010636:Phenols; D003300:Copper