Purification and properties of a feruloyl/ϱ-coumaroyl esterase from the fungus Penicillium pinophilum

Abstract

A purified extracellular phenolic acid esterase, produced by the fungus Penicillium pinophilum in solid-state culture, released ferulic and ϱ-coumaric acid from methyl esters of the acids. The esterase was also able to release all the alkali-extractable feruloyl and 80% of the ϱ-coumaroyl groups from a water-soluble wheat straw xylan without degrading the polysaccharide, but it showed no capacity to release ferulic and ϱ-coumaric acid from a grass cell wall preparation in the absence of other xylanolytic enzymes. Synergistic effects were observed between the esterase and other xylan-degrading enzymes in hydrolyzing the ferulic and, to a lesser extent, the ϱ-coumaric acid esters from both wheat straw xylan and the grass cell walls. The esterase had an apparent molecular mass of 57 kDa by SDS-PAGE and an isoelectric pH of 4.6: temperature and pH optima were 55°C and 6.0, respectively. Cu 2+ and Fe 2+ were inhibitory, but Zn 2+, Ca 2+, Ag +, and Mg 2+ stimulated activity. The enzyme had a higher affinity towards the methyl ester of ϱ-coumaric acid than towards the methyl ester of ferulic acid: the apparent K m values for the ferulic acid and ϱ-coumaric acid esters were 0.14 and 0.08 mM, respectively; the V max values were 32.5 and 37.9 μmol min -1 mg -1, respectively.