Metabolism of ferulic acid to vanillin. A bacterial gene of the enoyl-SCoA hydratase/isomerase superfamily encodes an enzyme for the hydration and cleavage of a hydroxycinnamic acid SCoA thioester.

A gene encoding a novel enoyl-SCoA hydratase/lyase enzyme for the hydration and nonoxidative cleavage of feruloyl-SCoA to vanillin and acetyl-SCoA was isolated and characterized from a strain of Pseudomonas fluorescens. Feruloyl-SCoA is the CoASH thioester of ferulic acid (4-hydroxy-3-methoxy-trans-cinnamic acid), an abundant constituent of plant cell walls and a degradation product of lignin. The gene was isolated by a combination of mutant complementation and biochemical approaches, and its function was demonstrated by heterologous expression in Escherichia coli under the control of a T7 RNA polymerase promoter. The gene product is a member of the enoyl-SCoA hydratase/isomerase superfamily.