InterPro domain: IPR005149

Phenolic acids, also called substituted hydroxycinnamic acids, are abundant in the plant kingdom because they are involved in the structure of plant cell walls and are present in some vacuoles. In plant-soil ecosystems they are released as free acids by hemicellulases produced by several fungi and bacteria. Of these weak acids, the most abundant are p-coumaric, ferulic, and caffeic acids, considered to be natural toxins that inhibit the growth of microorganisms, especially at low pHs. In spite of this chemical stress, some bacteria can use phenolic acids as a sole source of carbon. For other microorganisms, these compounds induce a specific response by which the organism adapts to its environment. The ubiquitous lactic acid bacterium Lactobacillus plantarum exhibits an inducible phenolic acid decarboxylase (PAD) activity which converts these substrates into less-toxic vinyl phenol derivatives. PadR acts as a repressor of padA gene expression in the phenolic acid stress response [ 1 ].

1. Cloning, deletion, and characterization of PadR, the transcriptional repressor of the phenolic acid decarboxylase-encoding padA gene of Lactobacillus plantarum. Appl. Environ. Microbiol. 70, 2146-53