Purification and Properties of a Feruloyl Esterase Involved in Lignocellulose Degradation by Aureobasidium pullulans

AUTOR(ES)
FONTE

American Society for Microbiology

RESUMO

The lignocellulolytic fungus Aureobasidium pullulans NRRL Y 2311-1 produces feruloyl esterase activity when grown on birchwood xylan. Feruloyl esterase was purified from culture supernatant by ultrafiltration and anion-exchange, hydrophobic interaction, and gel filtration chromatography. The pure enzyme is a monomer with an estimated molecular mass of 210 kDa in both native and denatured forms and has an apparent degree of glycosylation of 48%. The enzyme has a pI of 6.5, and maximum activity is observed at pH 6.7 and 60°C. Specific activities for methyl ferulate, methyl p-coumarate, methyl sinapate, and methyl caffeate are 21.6, 35.3, 12.9, and 30.4 μmol/min/mg, respectively. The pure feruloyl esterase transforms both 2-O and 5-O arabinofuranosidase-linked ferulate equally well and also shows high activity on the substrates 4-O-trans-feruloyl-xylopyranoside, O-{5-O-[(E)-feruloyl]-α-l-arabinofuranosyl}-(1,3)-O-β-d-xylopyranosyl-(1,4)-d-xylopyranose, and p-nitrophenyl-acetate but reveals only low activity on p-nitrophenyl-butyrate. The catalytic efficiency (kcat/Km) of the enzyme was highest on methyl p-coumarate of all the substrates tested. Sequencing revealed the following eight N-terminal amino acids: AVYTLDGD.

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