OleB from Bacterial Hydrocarbon Biosynthesis Is a β-Lactone Decarboxylase That Shares Key Features with Haloalkane Dehalogenases.

OleB is an α/β-hydrolase found in bacteria that biosynthesize long-chain olefinic hydrocarbons, but its function has remained obscure. We report that OleB from the Gram-negative bacterium Xanthomonas campestris performs an unprecedented β-lactone decarboxylation reaction, to complete cis-olefin biosynthesis. OleB reactions monitored by H nuclear magnetic resonance spectroscopy revealed a selectivity for decarboxylating cis-β-lactones and no discernible activity with trans-β-lactones, consistent with the known configuration of pathway intermediates.