title: Mechanism of O2 activation and substrate hydroxylation in noncoupled binuclear copper monooxygenases.
abstract: Peptidylglycine α-hydroxylating monooxygenase (PHM) and dopamine β-monooxygenase (DβM) are copper-dependent enzymes that are vital for neurotransmitter regulation and hormone biosynthesis. These enzymes feature a unique active site consisting of two spatially separated (by 11 Å in PHM) and magnetically noncoupled copper centers that enables 1e-activation of O2for hydrogen atom abstraction (HAA) of substrate C-H bonds and subsequent hydroxylation. Although the structures of the resting enzymes are known, details of the hydroxylation mechanism and timing of long-range electron transfer (ET) are not clear. This study presents density-functional calculations of the full reaction coordinate, which demonstrate: (i) the importance of the end-on coordination of superoxide to Cu for HAA along the triplet spin surface; (ii) substrate radical rebound to a CuIIhydroperoxide favors the proximal, nonprotonated oxygen; and (iii) long-range ET can only occur at a late step with a large driving force, which serves to inhibit deleterious Fenton chemistry. The large inner-sphere reorganization energy at the ET site is used as a control mechanism to arrest premature ET and dictate the correct timing of ET.
authors: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors: Ryan E
authors: RE
authors: Cowley
authors: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors: Li
authors: L
authors: Tian
authors: Department of Chemistry, Stanford University, Stanford, CA 94305; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025 edward.solomon@stanford.edu.
authors: Edward I
authors: EI
authors: Solomon
mesh_terms: D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D003300:Copper / Q000737:chemistry*; D004299:Dopamine beta-Hydroxylase / Q000737:chemistry*; D006801:Humans; D006859:Hydrogen / Q000737:chemistry*; D006900:Hydroxylation; D007700:Kinetics; D051379:Mice; D006899:Mixed Function Oxygenases / Q000737:chemistry*; D009097:Multienzyme Complexes / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011789:Quantum Theory; D051381:Rats; D013481:Superoxides / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D009097:Multienzyme Complexes; D013481:Superoxides; D003300:Copper; D006859:Hydrogen; D006899:Mixed Function Oxygenases; D004299:Dopamine beta-Hydroxylase; C035189:peptidylglycine monooxygenase; D010100:Oxygen
keywords: O2 activation; copper; electron transfer; reaction coordinates; reorganization energy