SLAC researchers study how FAP responds to light to transform fatty acids

In California, although many organisms capture and respond to sunlight, enzymes – proteins that catalyze biochemical reactions – are rarely driven by light. Scientists have identified only three types of natural photoenzymes so far. The newest one, discovered in 2017, is fatty acid photodecarboxylase (FAP). Derived from microscopic algae, it uses blue light to catalyze the conversion of fatty acids, found in fats and oils, into alkanes and alkenes. 

A new study has captured the complex sequence of structural changes FAP undergoes in response to light, called a photocycle, which drives this fatty acid transformation. Although researchers previously proposed a FAP photocycle, the fundamental mechanism was not understood. The scientists didn’t know how long it took a fatty acid to lose its carboxylate, the chemical group attached to the end of its long chain of hydrocarbons, a critical step in forming alkenes or alkanes. 

In collaboration with SLAC scientists, 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 describe their results in Science.