Abstract A neutral xylanase (XynII) from Volvariella
volvacea was identified and characterized. Unlike other
modular xylanases, it consists of only a single GH10 catalytic
domain with a unique C-terminal sequence (W-R-W-F)
and a phenylalanine and proline-rich motif (T-P-F-P-P-F) at
N-terminus, indicating that it is a novel GH10 xylanase.
XynII exhibited optimal activity at pH 7 and 60 C and
stability over a broad range of pH 4.0–10.0. XynII displayed
extreme highly SDS resistance retaining 101.98,
92.99, and 69.84 % activity at the presence of 300 mM
SDS on birchwood, soluble oat spelt, and beechwood
xylan, respectively. It remained largely intact after 24 h of
incubation with proteinase K at a protease to protein ratio
of 1:50 at 37 C. The kinetic constants Km value towards
beechwood xylan was 0.548 mg ml-1
, and the kcat/Km
ratio, reflecting the catalytic efficiency of the enzyme, was
126.42 ml mg-1 s
-1 at 60 C. XynII was a true endo-acting
xylanase lacking cellulase activity. It has weak activity
towards xylotriose but efficiently hydrolyzed xylans and
xylooligosaccharides larger than xylotriose mainly to
xylobiose. Synergistic action with acetyl xylan esterase
(AXEI) from V. volvacea was observed for de-starched
wheat bran. The highest degree of synergy (DS 1.42) was
obtained in sequential reactions with AXEI digestion preceding
XynII. The high SDS resistance and intrinsic stability
suggested XynII may have potential applications in
various industrial processes especially for the detergent and
textile industries and animal feed industries.
K