Abstract
Glucose oxidase (GO) and copper amine oxidase (CAO) catalyze the reduction of molecular oxygen to hydrogen peroxide. If a closed-shell cofactor (like FADH2 in GO and topaquinone (TPQ) in CAO) is electron donor in dioxygen reduction, the formation of a closed-shell species (H2O 2) is a spin forbidden process. Both in GO and CAO, formation of a superoxide ion that leads to the creation of a radical pair is experimentally suggested to be the rate-limiting step in the dioxygen reduction process. The present density functional theory (DFT) studies suggest that in GO, the creation of the radical pair induces a spin transition by spin orbit coupling (SOC) in O2 -(rad), whereas in CAO, it is induced by exchange interaction with the paramagnetic metal ion (Cu(II)). In the rate-limiting step, this spin-transition is suggested to transform the O 2 -(rad)-FADH2 +(rad) radical pair in GO and the Cu(II)-TPQ (triplet) species in CAO, from a triplet (T) to a singlet (S) state. For CAO, a mechanism for the O-O bond cleavage step in the biogenesis of TPQ is also suggested.
Original language | English (US) |
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Pages (from-to) | 173-178 |
Number of pages | 6 |
Journal | Biochimica et Biophysica Acta - Proteins and Proteomics |
Volume | 1647 |
Issue number | 1-2 |
DOIs | |
State | Published - Apr 11 2003 |
Externally published | Yes |
Keywords
- Copper amine oxidase
- Density functional theory
- Dioxygen activation
- Glucose oxidase
- Spin transition
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Genetics