Functional classification of the microbial feruloyl esterases.

Feruloyl esterases have potential uses over a broad range of applications in the agri-food industries. In recent years, the number of microbial feruloyl esterase activities reported has increased and, in parallel, even more related protein sequences may be discerned in the growing genome databases. Based on substrate utilisation data and supported by primary sequence identity, four sub-classes have been characterised and termed type-A, B, C and D. The proposed sub-classification scheme is discussed in terms of the evolutionary relationships existing between carbohydrate esterases

Identification of a type-D feruloyl esterase from Neurospora crassa.

Feruloyl esterases constitute an interesting group of enzymes that have the potential for use over a broad range of applications in the agri-food industries. In order to expand the range of available enzymes, we have examined the presence of feruoyl esterase genes present in the genome sequence of the filamentous fungus Neurospora crassa. We have identified an orphan gene (contig 3.544), the translation of which shows sequence identity with known feruloyl esterases. This gene was cloned and the corresponding recombinant protein expressed in Pichia pastoris to confirm that the enzyme (NcFaeD-3.544) exhibits feruloyl esterase activity. Unusually the enzyme was capable of p-coumaric acid release from untreated crude plant cell wall materials. The substrate utilisation preferences of the recombinant enzyme place it in the recently recognised type-D sub-class of feruloyl esterase