Researchers Discover New Property Of Enzymes

Researchers at Delft University of Technology and the South China University of Technology have discovered a surprising new property in a well-known group of enzymes, opening the door to cleaner and more sustainable chemical production. The discovery was unexpected: alcohol oxidases are not enzymes that are normally associated with acyl transfer chemistry. But in a new study, the researchers discovered, entirely by chance, that these enzymes can also perform a completely different type of chemical reaction, namely transesterification reactions. Transesterification is used on an industrial scale, for example in the production of biodiesel from pure vegetable oil. Based on follow-up research, the researchers were able to provide a mechanistic rationale for this behaviour, and in hindsight, the reactivity is becoming increasingly plausible. The research has been published in Nature Communications.

Water
What makes this discovery so remarkable is not only the reaction itself, but also where it takes place: in water. In traditional chemistry, transesterification in water is extremely difficult. Water tends to interfere and break molecules apart through a competing reaction called hydrolysis.

The key lies in the microscopic structure of the enzyme. Although the reaction takes place in water, the active site of the enzyme – the small pocket where the chemical reaction occurs – is highly hydrophobic, which means it repels water. This creates a kind of “dry bubble” in the enzyme. Water molecules are kept out, while the desired reactants are allowed in. As a result, the enzyme allows useful reactions to take place and prevents the unwanted degradation that normally occurs in water. In effect, the enzyme acts as a molecular bouncer, determining who gets access to the reaction site.

Applications
For the average person, this discovery will not change daily life overnight, but the long-term implications are significant. If chemists can carry out more reactions in water and under mild conditions, this could contribute to cleaner and less energy-intensive chemical production. This could translate into less hazardous solvents, less waste and lower energy input, benefits that are ultimately important for sustainability, costs and environmental impact.

Scientific curiosity
Beyond the specific finding, the study beautifully illustrates the importance of being open to unexpected results and contributes to our understanding of enzyme promiscuity. Enzyme promiscuity is the ability of an enzyme to catalyse a reaction other than the one for which it is specialised. Sometimes science advances not by following the plan, but by noticing what could not have happened and asking why it did happen.