Combining PET-degrading enzymes together speeds up the breakdown process sixfold

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Algemeen advies 02/10/2020 06:29
Two years ago, researchers at the University of Portsmouth in the UK and the NREL in the USA identified an enzyme capable of degrading PET, called PETase. Now, an enzyme found in the rubbish dwelling bacterium that lives on a diet of plastic bottles, has been combined with PETase to speed up the breakdown of plastic.

Two years ago, researchers at the University of Portsmouth in the UK and the NREL in the USA identified an enzyme capable of degrading PET, called PETase. Now, an enzyme found in the rubbish dwelling bacterium that lives on a diet of plastic bottles, has been combined with PETase to speed up the breakdown of plastic.

The team engineered the natural PETase enzyme in the laboratory to be around 20 percent faster at breaking down PET. Now, the same trans-Atlantic team have combined PETase and its ‘partner’, a second enzyme called MHETase, to generate much bigger improvements: Simply mixing PETase with MHETase doubled the speed of PET breakdown, and engineering a connection between the two enzymes to create a ‘super-enzyme’, increased this activity by a further three times.

The team was co-led by the scientists who engineered PETase, Professor John McGeehan, director of the centre for enzyme innovation (CEI) at the University of Portsmouth, and Dr Gregg Beckham, Senior Research Fellow at the National Renewable Energy Laboratory (NREL) in the US.

Professor McGeehan said “Gregg and I were chatting about how PETase attacks the surface of the plastics and MHETase chops things up further, so it seemed natural to see if we could use them together, mimicking what happens in nature.

The first experiments showed that the enzymes did indeed work better together, so the researchers decided to try to physically link them, like two Pac-men joined by a piece of string.

“It took a great deal of work on both sides of the Atlantic, but it was worth the effort – we were delighted to see that our new chimeric enzyme is up to three times faster than the naturally evolved separate enzymes, opening new avenues for further improvements.”

PETase and the new combined MHETase-PETase both work by digesting PET plastic, returning it to its original building blocks. This allows for plastics to be made and reused endlessly, reducing our reliance on fossil resources such as oil and gas.

Professor McGeehan used the Diamond Light Source, in Oxfordshire, a synchrotron that uses intense beams of X-rays 10 billion times brighter than the Sun to act as a microscope powerful enough to see individual atoms. This allowed the team to solve the 3D structure of the MHETase enzyme, giving them the molecular blueprints to begin engineering a faster enzyme system.

The new research combined structural, computational, biochemical and bioinformatics approaches to reveal molecular insights into its structure and how it functions. The study was a huge team effort involving scientists at all levels of their careers.

Professor John McGeehan: " It took a great deal of work on both sides of the Atlantic, but it was worth the effort"

https://www.port.ac.uk



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