Abstract
BackgroundL-Amino acid oxidases (LAOs) have been generally described as flavoproteins that oxidize amino acids releasing the corresponding ketoacid, ammonium and hydrogen peroxide. The generation of hydrogen peroxide gives to these enzymes antimicrobial characteristics. They are involved in processes such as biofilm development and microbial competition. LAOs are of great biotechnological interest in different applications such as the design of biosensors, biotransformations and biomedicine.The marine bacterium Marinomonas mediterranea synthesizes LodA, the first known LAO that contains a quinone cofactor. LodA is encoded in an operon that contains a second gene coding for LodB, a protein required for the post-translational modification generating the cofactor. Recently, GoxA, a quinoprotein with sequence similarity to LodA but with a different enzymatic activity (glycine oxidase instead of lysine-ε-oxidase) has been described. The aim of this work has been to study the distribution of genes similar to lodA and/or goxA in sequenced microbial genomes and to get insight into the evolution of this novel family of proteins through phylogenetic analysis.ResultsGenes encoding LodA-like proteins have been detected in several bacterial classes. However, they are absent in Archaea and detected only in a small group of fungi of the class Agaromycetes. The vast majority of the genes detected are in a genome region with a nearby lodB-like gene suggesting a specific interaction between both partner proteins.Sequence alignment of the LodA-like proteins allowed the detection of several conserved residues. All of them showed a Cys and a Trp that aligned with the residues that are forming part of the cysteine tryptophilquinone (CTQ) cofactor in LodA. Phylogenetic analysis revealed that LodA-like proteins can be clustered in different groups. Interestingly, LodA and GoxA are in different groups, indicating that those groups are related to the enzymatic activity of the proteins detected.ConclusionsGenome mining has revealed for the first time the broad distribution of LodA-like proteins containing a CTQ cofactor in many different microbial groups. This study provides a platform to explore the potentially novel enzymatic activities of the proteins detected, the mechanisms of post-translational modifications involved in their synthesis, as well as their biological relevance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1455-y) contains supplementary material, which is available to authorized users.
Highlights
L-Amino acid oxidases (LAOs) have been generally described as flavoproteins that oxidize amino acids releasing the corresponding ketoacid, ammonium and hydrogen peroxide
Identification of genes similar to lodA and/or goxA in microbial genomes Using as query the sequence of the two M. mediterranea quinoproteins with amino acid oxidase activity: LodA [5] and GoxA [13], BLASTP search was performed against sequenced microbial genomes deposited in the Integrated Microbial Genomes database as of January 8, 2014
Our results indicate that proteins in the group IA show L-amino acid oxidase activity and that this capacity confers to them antimicrobial properties
Summary
L-Amino acid oxidases (LAOs) have been generally described as flavoproteins that oxidize amino acids releasing the corresponding ketoacid, ammonium and hydrogen peroxide. L-Amino acid oxidases (LAOs) are enzymes which oxidize amino acids releasing the corresponding ketoacid, ammonium and hydrogen peroxide. They have been found in different microbial groups including bacteria [1,2] the most studied members of this group are the LAOs present in snake venoms [3]. Enzymes oxidizing amino acids are of great biotechnological interest in many different fields such as the design of biosensors, processes of biotransformation and biomedicine [1]. It has been demonstrated that LodB, a flavoprotein encoded in the same operon as LodA, is involved in the post-translational modification that generates the quinone cofactor [9,10]
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