Surprising behavior of a fatty acid enzyme with potential biofuel applications

Derived from microscopic algae, the rare, light-driven enzyme converts fatty acids into starting ingredients for solvents and fuels.

Although many organisms capture and respond to sunlight, it’s rare to find enzymes – proteins that promote chemical reactions in living things – that are driven by light. Scientists have identified only three so far. The newest one, discovered in 2017, is called fatty acid photodecarboxylase (FAP). Derived from microscopic algae, FAP uses blue light to convert fatty acids into hydrocarbons that are similar to those found in crude oil.

“A growing number of researchers envision using FAPs for green chemistry applications because they can efficiently produce important components of solvents and fuels, including gasoline and jet fuels.” says Martin Weik, the leader of a research group at the Institut de Biologie Structurale at the Université Grenoble Alpes.

Weik is one of the primary investigators in a new study that has captured the complex sequence of structural changes, or photocycle, that FAP undergoes in response to light, which drives this fatty acid transformation. Researchers had proposed a possible FAP photocycle, but the fundamental mechanism was not understood, partly because the process is so fast that it’s very difficult to measure. Specifically, scientists didn’t know how long it took FAP to split a fatty acid and release a hydrocarbon molecule.

Experiments at the Linac Coherent Light Source (LCLS) at the Department of Energy’s SLAC National Accelerator Laboratory helped answer many of these outstanding questions. The researchers described their results in Science.

Read more on the SLAC website

Image: A study using SLAC’s LCLS X-ray laser captured how light drives a series of complex structural changes in an enzyme called FAP, which catalyzes the transformation of fatty acids into starting ingredients for solvents and fuels. This drawing captures the starting state of the catalytic reaction. The dark green background represents the protein’s molecular structure. The enzyme’s light-sensing part, called the FAD cofactor, is shown at center right with its three rings absorbing a photon coming from bottom left. A fatty acid at upper left awaits transformation. The amino acid shown at middle left plays an important role in the catalytic cycle, and the red dot near the center is a water molecule.

Credit: Damien Sorigué/Université Aix-Marseille