Unraveling the Conversion of Fatty Acids into Terminal Alkenes by an Integral Membrane Enzyme, UndB

Abstract

Biosynthetically produced 1-alkenes hold immense value as green alternatives to fossil fuels and find widespread applications in the polymer, lubricant, and detergent industries. UndB is the only known membrane enzyme capable of converting fatty acids into 1-alkenes with unprecedented in vivo titers. However, despite diverse applications, UndB has remained poorly understood since its discovery nearly a decade ago. We present here insights into the molecular basis of UndB catalysis and the mechanism of the UndB reaction at the membrane interface. We unravel UndB as a diiron-enzyme that utilizes a conserved histidine cluster at the active site. We decipher the dependency of UndB activity on molecular oxygen and electrons and identify the most efficient redox partners of UndB. We elucidate the catalytic intricacies of UndB and establish it as the most efficient decarboxylase in producing industrially valuable medium-chain 1-alkenes. We further identify CO2 as the C1-derived coproduct of the UndB-catalyzed reaction and provide compelling evidence supporting the hydrogen atom transfer mechanism of UndB. These results now place our understanding of UndB on a molecular level, paving the way for its application for sustainable 1-alkene production.