Abstract
SUMMARYResearch backgroundIn recent decades, laccases (p-diphenol-dioxygen oxidoreductases; EC 1.10.3.2) have attracted the attention of researchers due to their wide range of biotechnological and industrial applications. Laccases can oxidize a variety of organic and inorganic compounds, making them suitable as biocatalysts in biotechnological processes. Even though the most traditionally used laccases in the industry are of fungal origin, bacterial laccases have shown an enormous potential given their ability to act on several substrates and in multiple conditions. The present study aims to characterize a plasmid-encoded laccase-like multicopper oxidase (LMCO) from Ochrobactrum sp. BF15, a bacterial strain previously isolated from polluted soil.Experimental approachWe used in silico profile hidden Markov models to identify novel laccase-like genes in Ochrobactrum sp. BF15. For laccase characterization, we performed heterologous expression in Escherichia coli, purification and activity measurement on typical laccase substrates.Results and conclusionsProfile hidden Markov models allowed us to identify a novel LMCO, named Lac80. In silico analysis of Lac80 revealed the presence of three conserved copper oxidase domains characteristic of three-domain laccases. We successfully expressed Lac80 heterologously in E. coli, allowing us to purify the protein for further activity evaluation. Of thirteen typical laccase substrates tested, Lac80 showed lower activity on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), pyrocatechol, pyrogallol and vanillic acid, and higher activity on 2,6-dimethoxyphenol.Novelty and scientific contributionOur results show Lac80 as a promising laccase for use in industrial applications. The present work shows the relevance of bacterial laccases and highlights the importance of environmental plasmids as valuable sources of new genes encoding enzymes with potential use in biotechnological processes.
Highlights
Enzymes traditionally known as laccases are multicopper oxidases that catalyse the oxidation of a wide range of substrates and the simultaneous reduction of molecular oxygen to water
The present work shows the relevance of bacterial laccases and highlights the importance of environmental plasmids as valuable sources of new genes encoding enzymes with potential use in biotechnological processes
To identify novel LMCO-encoding genes in the plasmid dataset from the 35 strains previously isolated from a biopurification system [20], a profile Hidden Markov models-based search was performed
Summary
Enzymes traditionally known as laccases are multicopper oxidases that catalyse the oxidation of a wide range of substrates and the simultaneous reduction of molecular oxygen to water. Due to their ability to oxidize a wide variety of phenolic and non-phenolic compounds, they have been extensively used in biotechnological processes as biocatalysts They were recently renamed “laccase-like multicopper oxidases” (LMCOs), following the nomenclature revision of this enormously diverse group of enzymes [3]. A computational study analyzing over 2,000 bacterial genomes predicted the presence of laccase-like encoding genes in 36 % of the screened organisms [9] including autotrophic, alkalophilic, and even anaerobic bacteria [10], highlighting the extraordinary potential of bacteria as a source of novel LMCOs and pointing out the need to continue exploring the genome of these microorganisms
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