This family consists of several bacterial phenolic acid decarboxylase proteins. Phenolic acids, also called substituted cinnamic acids, are important lignin-related aromatic acids and natural constituents of plant cell walls. These acids (particularly ferulic, p-coumaric, and caffeic acids) bind the complex lignin polymer to the hemicellulose and cellulose in plants. The Phenolic acid decarboxylase (PAD) gene (pad) is transcriptionally regulated by p-coumaric, ferulic, or caffeic acid; these three acids are the three substrates of PAD [1].

1: Gene cloning, transcriptional analysis, purification, and characterization of phenolic acid decarboxylase from Bacillus subtilis. Cavin JF, Dartois V, Divies C; Appl Environ Microbiol 1998;64:1466-1471. PMID:9546183