PURIFICATION AND CHARACTERIZATION OF A FERULIC ACID DECARBOXYLASE FROM PSEUDOMONAS-FLUORESCENS

A ferulic acid decarboxylase enzyme which catalyzes the decarboxylatio n of ferulic acid to 4-hydroxy-3-methoxystyrene was purified from Pseu domonas fluorescens UI 670. The enzyme requires no cofactors and conta ins no prosthetic groups. Gel filtration estimated an apparent molecul ar mass of 40.4 (+/-6%) kDa, whereas sodium dodecyl sulfate-polyacryla mide gel electrophoresis showed a molecular mass of 20.4 kDa, indicati ng that ferulic acid decarboxylase is a homodimer in solution. The pur ified enzyme displayed an optimum temperature range of 27 to 30 degree s C, exhibited an optimum pH of 7.3 in potassium phosphate buffer, and had a K-m of 7.9 mM for ferulic acid. This enzyme also decarboxylated 4-hydroxycinnamic acid but not 2- or 3-hydroxycinnamic acid, indicati ng that a hydroxy group para to the carboxylic acid-containing side ch ain is required for the enzymatic reaction. The enzyme was inactivated by Hg2+, CU2+, p-chloromercuribenzoic acid, and N-ethylmaleimide, sug gesting that sulfhydryl groups are necessary for enzyme activity. Diet hyl pyrocarbonate, a histidine-specific inhibitor, did not affect enzy me activity.