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Publication Abstract from PubMed

The aaoso gene from Streptococcus oligofermentas encodes for a 43 kDa flavoprotein (SoAAO), which was reported to possess a low catalytic activity versus several different L-amino acids: accordingly, it was classified as an L-amino acid oxidase. Subsequently, SoAAO was demonstrated to oxidize aminoacetone (a prooxidant metabolite), with an activity about 25-folds higher than the activity displayed on L-lysine this yielding support to the assumption of aminoacetone as the preferred substrate. In this work we present a characterization of the SoAAO structure-function relationships. SoAAO is a FAD-containing enzyme that does not possess the classical properties of 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 alpha/beta domain corresponding to the FAD-binding domain, a beta-domain partially modulating accessibility to the coenzyme, and an additional alpha-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 held to facilitate the condensation reaction. A specialized role for SoAAO in the microbial defence mechanism related to aminoacetone catabolism through a mechanism yielding dimethylpyrazine derivatives instead of methylglyoxal can be proposed.

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 Biochem J. 2014 Sep 30. PMID:25269103^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.