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Researchers from the Manchester Institute of Biotechnology and the Department of Chemistry at The University of Manchester have described a novel enzyme that could significantly change the way essential chemicals and medicines are made.

Published in Nature, this centers on a process called nucleophilic aromatic substitution (S_NAr), a class of transformation that is widely used across the chemical industries including pharmaceuticals and agrochemicals. This enzymatic process offers a greener, more efficient alternative to traditional chemical synthesis.

Catalyzing chemistry

S_NAr reactions are crucial in manufacturing many valuable products such as medicines and agrochemicals. However, conventional methods for carrying out these reactions come with major challenges. They often require harsh conditions like high temperatures and environmentally harmful solvents.

Established methods of performing S_NAr chemistry often produce compounds as isomeric—two or more compounds that have the same chemical formula but different arrangements of the atoms—mixtures, necessitating the use of expensive and time-consuming purification steps.

To overcome these hurdles, a team of researchers, led by Professor Anthony Green and Professor Igor Larrosa, have used directed evolution to develop a new enzyme capable of catalyzing S_NAr processes. This new enzyme, named S_NAr1.3, performs a range of S_NAr reactions with high efficiency and selectivity under mild reaction conditions. Unlike traditional chemical methods, this enzyme operates in water-based solutions at moderate temperatures, reducing the environmental impact and energy required.

How it works

As there is no known natural enzyme that could catalyze S_NAr reactions, the team initially discovered that an enzyme previously developed in their laboratory for a different chemical transformation could also perform S_NAr chemistry, albeit with modest efficiency and selectivity. By using automated directed evolution, the researchers were able to further engineer this enzyme to have the desired characteristics.

The team evaluated more than 4,000 clones before identifying an enzyme S_NAr1.3 that contains six mutations and is 160-fold more active than the parent enzyme. This enzyme efficiently promotes a wide variety of S_NAr processes and can generate target products in a single mirror-image form, which is crucial for applications in the pharmaceutical sector.

"This enzyme could be transformative for industry. It not only speeds up a crucial class of chemical transformation, but does so with remarkable precision, even when working with challenging chemical building blocks. This opens up new possibilities for creating complex, valuable molecules with better environmental credentials and lower costs," says Professor Anthony Green, Director of the MIB.

The benefits of S_NAr1.3

S_NAr1.3 has a number of features that make it an attractive option for chemical production:

• Efficiency: the enzyme can perform more than 4,000 reaction cycles without losing effectiveness, making it highly productive.
• Precision: it creates molecules in a single mirror-image form, which is critical for the safety and effectiveness of medicines.
• Versatility: S_NAr1.3 works with a wide range of chemical building blocks, enabling the creation of complex structures like quaternary carbon centers—a common feature in advanced drugs.
• Sustainability: operating under mild, water-based conditions, the enzyme reduces the need for harmful chemicals and energy-intensive processes, making it an environmentally friendly alternative.

The team's work also sheds light on the enzyme's inner workings. Using advanced analytic techniques, they uncovered how S_NAr1.3's unique structure allows it to bind and position chemicals precisely, enabling its exceptional performance. These insights provide a blueprint for designing even more powerful enzymes in the future.

A greener future for industry

The development of S_NAr1.3 highlights the potential of biocatalysis and provides a template for future development. As the world moves towards net zero, and industry is looking for ways to improve efficiency and reduce its environmental impact, biotechnology could be the answer to these pressing challenges.

"This is a landmark achievement in biocatalysis," said Larrosa, Professor and Chair in Organic Chemistry at The University of Manchester. "It demonstrates how we can harness and even improve on nature's tools to address some of the toughest challenges in modern chemistry."

What's next?

While S_NAr1.3 is already showing immense promise, the researchers believe this is just the beginning. With further refinement, the enzyme could be adapted for even more complex reactions, making it a valuable tool in drug development, agricultural chemicals, and materials science.

"The possibilities are just starting to emerge," said Professor Green. "By combining modern protein design with high-throughput testing, we're optimistic about creating a new generation of enzymes that can revolutionize S_NAr chemistry."

This research offers a glimpse into a future where manufacturing essential products is cleaner, cheaper, and more efficient. For industries looking to reduce their environmental impact while maintaining high standards of quality, S_NAr1.3 represents a promising solution.