Abstract
The marine environment is a rich source of antimicrobial compounds with promising pharmaceutical and biotechnological applications. The Pseudoalteromonas genus harbors one of the highest proportions of bacterial species producing antimicrobial molecules. For decades, the presence of proteins with L-amino acid oxidase (LAAO) and antimicrobial activity in Pseudoalteromonas luteoviolacea has been known. Here, we present for the first time the identification, cloning, characterization and phylogenetic analysis of Pl-LAAO, the enzyme responsible for both LAAO and antimicrobial activity in P. luteoviolacea strain CPMOR-2. Pl-LAAO is a flavoprotein of a broad substrate range, in which the hydrogen peroxide generated in the LAAO reaction is responsible for the antimicrobial activity. So far, no protein with a sequence similarity to Pl-LAAO has been cloned or characterized, with this being the first report on a flavin adenine dinucleotide (FAD)-containing LAAO with antimicrobial activity from a marine microorganism. Our results revealed that 20.4% of the sequenced Pseudoalteromonas strains (specifically, 66.6% of P. luteoviolacea strains) contain Pl-laao similar genes, which constitutes a well-defined phylogenetic group. In summary, this work provides insights into the biological significance of antimicrobial LAAOs in the Pseudoalteromonas genus and shows an effective approach for the detection of novel LAAOs, whose study may be useful for biotechnological applications.
Highlights
Marine ecological niches are excellent sources for many bioactive compounds of biotechnological and pharmaceutical interest
We report for the first time the identification, cloning, and heterologous expression of the gene encoding this antimicrobial protein in P. luteoviolacea CPMOR-2, which has been named Pl-L-amino acid oxidase (LAAO)
Pl-LAAO is a flavoprotein of 653 amino acids that possesses L-amino acid oxidase activity with a broad substrate range (Figure 4)
Summary
Marine ecological niches are excellent sources for many bioactive compounds of biotechnological and pharmaceutical interest. Antimicrobial compounds synthetized by marine organisms offer a promising alternative to antibiotics [1]. Microorganisms from the Pseudoalteromonas genus are well-known producers of several metabolites with antimicrobial activity, such as alkaloids, polyketides, peptides, and proteins [2,3]. The genus Pseudoalteromonas includes Gram-negative, heterotrophic, and aerobic marine bacteria, which belong to the Alteromonadales order in the Gammaproteobacteria class. They are commonly found in association with seawater macroorganisms, where they play a critical role in holobiont homeostasis through their metabolic activities [2]. Pseudoalteromonas luteoviolacea was described in 1976, and was reported to produce antibacterial polyanionic substances inhibited by catalase
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