Aminoacetone Oxidase from Streptococcus Oligofermentas Belongs to a New Three-Domain Family of Bacterial Flavoproteins.Molla, G., Nardini, M., Motta, P., D'Arrigo, P., Panzeri, W., Pollegioni, L.
(2014) Biochem J 464: 387
- PubMed: 25269103
- DOI: https://doi.org/10.1042/BJ20140972
- Primary Citation of Related Structures:
- PubMed Abstract:
The aaoSo gene from Streptococcus oligofermentans encodes a 43 kDa flavoprotein, aminoacetone oxidase (SoAAO), which was reported to possess a low catalytic activity against several different L-amino acids; accordingly, it was classified as an L-amino acid oxidase. Subsequently, SoAAO was demonstrated to oxidize aminoacetone (a pro-oxidant metabolite), with an activity ~25-fold higher than the activity displayed on L-lysine, thus lending support to the assumption of aminoacetone as the preferred substrate. In the present study, we have characterized the SoAAO structure-function relationship. SoAAO is an FAD-containing enzyme that does not possess the classical properties of the oxidase/dehydrogenase class of flavoproteins (i.e. no flavin semiquinone formation is observed during anaerobic photoreduction as well as no reaction with sulfite) and does not show a true L-amino acid oxidase activity. From a structural point of view, SoAAO belongs to a novel protein family composed of three domains: an α/β domain corresponding to the FAD-binding domain, a β-domain partially modulating accessibility to the coenzyme, and an additional α-domain. Analysis of the reaction products of SoAAO on aminoacetone showed 2,5-dimethylpyrazine as the main product; we propose that condensation of two aminoacetone molecules yields 3,6-dimethyl-2,5-dihydropyrazine that is subsequently oxidized to 2,5-dimethylpyrazine. The ability of SoAAO to bind two molecules of the substrate analogue O-methylglycine ligand is thought to facilitate the condensation reaction. A specialized role for SoAAO in the microbial defence mechanism related to aminoacetone catabolism through a pathway yielding dimethylpyrazine derivatives instead of methylglyoxal can be proposed.
†The Protein Factory, Centro Interuniversitario di Biotecnologie Proteiche, Politecnico di Milano, ICRM CNR Milano, and Università degli Studi deII'Insubria, Varese, Italy.