Artificial manganese metalloenzymes with laccase-like activity: Design, Synthesis and Characterization

Laccase is an oxidase of great industrial interest due to its ability to catalyse oxidation processes of phenols and persistent organic pollutants. However, it is susceptible to denaturation at high temperatures, sensitive to pH and in the presence of high concentrations of solvents, which is a problem for industrial use. To solve this problem, this work develops the synthesis in aqueous medium of a new Mn metalloenzyme with laccase oxidase mimetic catalytic activity. To do this, Geobacillus thermocatenulatus lipase (GTL) is used as a "scaffold" enzyme, which is mixed with a manganese salt at 50ºC in an aqueous medium. This produces in situ formation of manganese (IV) oxide nanowires that interact with the enzyme, obtaining the GTL-Mn bionanohybrid. On the other hand, its oxidative activity was evaluated using the ABTS assay, obtaining a catalytic efficiency 300 times greater than the laccase from Trametes versicolor. These new Mn-metalloenzyme turned out to be 2 times more stable at 40 ºC, 3 times more stable in the presence of 10% acetonitrile and 10 times more stable at 20% acetonitrile than laccase Novozym 51003®. Furthermore, the site-selective immobilized GTL-Mn showed much higher stability then the soluble form. Oxidase-like activity of these Mn-metalloenzyme was successfully performed against other substrates such as L-DOPA or phloridzin in oligomerization reactions.