Book chapter
Toward understanding the mechanism of oxygen activation by flavoprotein oxidases
Walter De Gruyter
01 Jan 2013
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
Several common themes have emerged from our recent studies on the mechanism of oxygen activation by monomeric sarcosine oxidase (MSOX), N-methyltryptophan oxidase (MTOX), and heterotetrameric sarcosine oxidase (TSOX). MSOX and MTOX are members of a family of monomeric amino acid oxidases that contain 1 mol of covalently bound FAD. TSOX is a bifunctional, multimeric (alpha beta gamma delta) enzyme that contains 1 mol each of noncovalently bound FAD and covalently bound FMN. FAD is bound to the beta-subunit which exhibits structural and sequence homology with MSOX and MTOX; FMN is located at the interface between the TSOX alpha- and beta-subunits. MSOX and MTOX contain separate sites for amino acid oxidation and oxygen reduction above opposite sides of the flavin ring (re- and si-face, respectively). The corresponding sites in TSOX are located at different flavins (FAD and FMN, respectively). A single basic residue is solely responsible for oxygen activation by MSOX and MTOX (Lys265 and Lys259, respectively), similar to that previously observed for His516 in glucose oxidase. Oxygen activation by TSOX is mediated by a pair of basic residues (beta Lys172, beta Lys278). An unobstructed or gated tunnel provides a postulated route for oxygen diffusion to the active site in TSOX and MSOX, respectively. Chloride acts as a putative oxygen surrogate that binds to the side chain of Lys265 in MSOX or His516 in glucose oxidase. The positively charged residues at the oxygen activation sites in MSOX, MTOX, TSOX, and glucose oxidase provide an apparent pre-organized binding site for superoxide anion that accelerates the critical initial 1-electron reduction of oxygen by lowering the reorganization energy of the reaction. Comparison with other enzymes indicates that, although electrostatic catalysis is frequently a contributing factor, flavo-oxidases exhibit considerable diversity in the mechanism of oxygen activation, as discussed.
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Details
- Title
- Toward understanding the mechanism of oxygen activation by flavoprotein oxidases
- Creators
- Marilyn Schuman Jorns
- Contributors
- R Hille (Editor)S M Miller (Editor)B Palfey (Editor)
- Publisher
- Walter De Gruyter; BERLIN
- Number of pages
- 17
- Resource Type
- Book chapter
- Language
- English
- Academic Unit
- [Retired Faculty]
- Identifiers
- 991019170439604721
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- Biochemistry & Molecular Biology