Characterisation of feruloyl esterase activity in barley

Feruloyl esterase activity has been detected in barley grain and germinated barley. No differences have been found between the values of activity against methyl ferulate in barley crude extracts (1.05 ± 0.10 mU mg^-1 protein) with and without sterilisation (P > 0.05), indicating that the activity is native to the barley grain rather than due to microbial contamination. The highest value of esterase activity was detected after 2 day growth, although an overall downward trend was observed over a 6 day germination period at 25°C. The K(m) and V(max) of the crude barley esterase/s on methyl ferulate were 0.34 ± 0.05 mM and 0.76 ± 0.03 mU mg^-1 protein, respectively. The crude extracts were also active upon the methyl esters of sinapic, p-coumaric and caffeic acids, and upon a feruloylated arabino-oligosaccharide (Ara₂F), but not upon the methyl ester of vanillic acid.