HMN 2026: How Engineered enzymes enable greener one-pot amide synthesis for drug manufacturing

A single type of chemical structure that shows up again and again in modern medicine is the amide bond that links a carbonyl group (C=O) to a nitrogen atom. They’re so ubiquitous that 117 of the top 200 small-molecule drugs by retail sales in 2023 feature at least one amide bond. And now, researchers have discovered a clever new way to reengineer natural enzymes to build amides from simple chemicals like aldehydes and amines.

The team chose a naturally abundant enzyme family called aldehyde dehydrogenases (ALDHs), specifically p-hydroxybenzaldehyde dehydrogenase (PHBDD), which can efficiently convert aldehydes into acids. The team turned it into a new catalyst, known as an oxidative amidase (OxiAm), by modifying its internal pocket of the enzyme in two major ways: making it hydrophobic to prevent the formation of unwanted acids and making it bigger to allow larger, diverse chemical parts to fit inside so they could be bonded together.

According to the results published in Science, the team was able to obtain amides directly from commercially available alcohols via a two-step enzymatic cascade reaction carried out in a single container. This approach could enable new, greener methods for producing five major drug molecules, including a key component of imatinib, an essential drug used to treat chronic myeloid leukemia and gastrointestinal stromal tumors.

Shortcut to the backbone of medicinal molecules

Amide bonds make an appearance in many well-known drugs used for treating cancer, heart disease, and blood disorders. Despite their importance, the way these bonds are typically formed is far from ideal. Most traditional ways of making amide bonds rely on highly reactive chemicals, harsh temperatures, or toxic metals, which create a lot of waste and make drug manufacturing less sustainable.

Switching to enzyme-based methods made the process eco-friendly but came with its own share of limitations. For example, lipases, enzymes commonly used to convert esters into amides, are active only with a narrow range of substrates. Other enzymes, such as ligases, require very high energy inputs to function properly.

The team overcame the limitations of traditional chemistry by leveraging the power of protein engineering and transforming a natural enzyme into a high-efficiency synthetic tool.

To achieve this, the researchers redesigned the PHBDD’s internal pocket. They removed the water-loving parts of the enzyme, two key positions, R166 and E259, and replaced them with water-repelling methionine and leucine. This change redirects the reaction, causing the enzyme to use an amine rather than water and to form an amide bond rather than an unwanted acid.

Another issue with ALDHs like PHBDD is that many important drug building blocks were too large to fit into their active site. After several attempts, the researchers identified that the tunnel can be enlarged by mutating a specific spot (T234G), widening the access tunnel from 6.1 to 8.1 Å.

The researchers paired their new OxiAm enzyme with alcohol dehydrogenase to create a one-pot, two-step process that turned common alcohols directly into amides using only oxygen from the air to drive the reaction. They then used this approach to test the production of five important pharmaceutical precursors: Vadadustat (an anemia drug), Imatinib (a leukemia drug), Lazabemide (a Parkinson’s disease drug), Saruparib (a cancer drug), and Vorinostat (a T-cell lymphoma drug).

This study is a great example of how clever tweaks in protein molecules via enzyme engineering can advance pharmaceutical manufacturing through biocatalytic synthesis.

The researchers believe this strategy provides a green and versatile platform for synthesizing structurally diverse amides with applications beyond medicine.

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