Different Photons, Same Chemistry: Identical Mechanism and Efficiency of Fatty Acid Photodecarboxylase under Blue and UV Excitation

Abstract

Fatty acid photodecarboxylase (FAP) is a promising photoenzyme for light‑driven hydrocarbon synthesis and a versatile chassis for photobiocatalysis. A recent study proposed that UV/violet illumination enhances FAP activity relative to blue light by accessing a distinct, more efficient photochemical regime. Here, steady-state and time‑resolved fluorescence, transient absorption spectroscopy under single‑turnover conditions, and product quantification under continuous irradiation show that the quantum yield of decarboxylation, the identities and kinetics of reaction intermediates, and the overall chemical yield are identical for blue and UV/violet excitation. These findings establish that FAP operates through a single, wavelength‑independent photocycle, overturning the proposed “violet‑enhanced” reactivity model.