New enzyme by directed evolution

Oeiras, 27.07.2015

Mimicking evolution and natural selection, researchers from the Lab of Microbial and Enzyme Technology were able to turn a metallo-oxidade from the hypertermophile Aquifex aeolicus into a laccase, which is 100-fold more efficient oxidizing organic substrates than metal ions, thus enlarging its range of biotechnological applications. The work is published ahead of print in ACS Catalysis from the American Chemical Society.

The starting point of this research was an enzyme, functional and stable at very high temperatures (mid point at 75oC), with the ability to oxidize metals such as Cu(I) and Fe(II). The end point is another enzyme, soluble, even more robust, which has the extra ability to oxidize aromatic organic compounds, non-phenolic, phenolic or synthetic dyes at a higher efficiency than metals. The process that turns the starting point into the end point is laboratory directed evolution. With this technique, the DNA coding for the Aquifex aeolicus metallo-oxidase was randomly mutated and the mutated enzymes were screened for their ability to oxidize organic compounds. The best performing enzyme was submitted to an extra round of mutation and selection. After four rounds and 94,000 enzymes tested, researches ended up with a new laccase: more efficient for degrading aromatic compounds, partially able to oxidize metals, more soluble and more thermodynamically stable than the original enzyme.

Laccases are considered the “greenest” enzymes in biotechnology because they use oxygen and have water as the only by-product. They find applications in the valorization of biomass, an alternative to fossil materials for the production of chemicals, materials, and fuel. Increasing the substrate range of an intrinsically robust enzyme from a hyperthermophile means increasing the application range in industrial settings. “What this works shows is that laboratory directed evolution is a powerful tool for the modification of biocatalysts and thus for efficient and more sustainable industrial options, which create the XXI century bio-economy“, says Lígia Martins who coordinated the study.

Original Paper

ACS Catalysis (2015) 5: 4932-4941

Turning a Hyperthermostable Metallo-oxidase into a Laccase by Directed Evolution

Vania Brissos , Maura Ferreira , Gregor Grass , and Ligia O. Martins