Purification and characterization of an inducible p-coumaric acid decarboxylase from Lactobacillus plantarum

Lactobacillus plantarum cells displayed substrate-inducible decarboxylase activities on p-coumaric and ferulic acids of 0.6 and 0.01 micromole min-1 mg-1, respectively. Activity in uninduced cells or corresponding cell extracts was undetectable (< 10-4 micromole min-1 mg-1). Specificity of induction indicates that at least two phenolic acid decarboxylases are produced in this bacterium. SDS-PAGE of partially purified protein extract from p-coumaric acid-induced cells showed one band of 23.5 kDa that was absent in the extract from uninduced cells. The native molecular mass of 93 kDa indicates that the enzyme is a homotetramer. The 1276-fold purified enzyme had a Km of 1.4 mM, a Vm of about 766 micromole min-1 mg-1, and a Kcat of 10(3)S-1 for p-coumaric and caffeic acids, but did not display any detectable activity on ferulic acid. Maximum activity was at 30 degrees C, at pH 5.5-6. Cofactors or metal ions were not required for activity.