Scientists have discovered new properties in plant enzymes that can influence the design of new chemical catalysts.
Enzymes catalyze or start one of the main chemical reactions needed for the synthesis of various organic molecules, including those used in lubricants, cosmetics and as a raw material for plastic production.
This enzyme can inspire new forms of green chemistry, say the researchers. we can adapt this biomolecule to make useful chemicals in plants, or use it as a basis for the development of new inspired catalysts to replace the more expensive toxic catalysts currently used.
The team discovered as part of ongoing research on enzymes that desaturate vegetable oils. This desaturase enzyme separates hydrogen atoms from certain carbon atoms that are close together in the hydrocarbon chain and inserts a double bond between these carbon atoms.
Before, the research team had developed a version of the mutated desaturase enzyme with interesting properties and studied the three mutations to see what each mutation would do.
Two single mutant enzymes cut the double bonds between adjacent carbon atoms and add “OH” (hydroxyl groups) to each carbon to form fatty acids with two adjacent hydroxyl groups.
Fatty acids containing adjacent OH groups, called diols, are important chemical components for the production of lubricants because they help in the smooth operation of hot engines. They can also be processed into building blocks for the production of plastic or other raw materials.
The best industrial catalyst for this reaction is expensive, volatile and toxic. Another problem is that there are various forms of diol and it is difficult for chemists to make a single pure form.
Mutant enzymes found to form a form so that they can be used without further processing or wastage.
Tracking the origin of oxygen atoms in the two OH groups reveals that both are from the same oxygen molecule (O2). The ability to transfer two oxygen atoms from the O2 molecule during a reaction known as “dioxygenase”, is something for the “diiron” enzyme (one with two iron atoms in the active site).
The diiron enzyme was not before reported to have the chemical dioxygenase. We had to do some difficult experiments to provide conclusive proof that this happened, and without Ed Whittel’s creativity and tenacity we would not have completed this study.
The next team’s goal is to get the crystal structure of this enzyme using X-rays at National Synchrotron Light Source II (NSLS-II), a user facility from the DOE Office of Science at the Brookhaven Laboratory.
We will share this structural information with our colleagues in computational chemistry to understand how this unprecedented chemistry can work with this class of catalysts.
This work can help the team control the configuration of laboratory-made catalysts to mimic the factory-produced version.
If we can integrate what we have learned into the design of industrial catalysts, this reaction can produce cleaner products with less waste and avoid the use of toxic chemicals.