A family 11 xylanase from Penicillium funiculosum is strongly inhibited by three wheat xylanase inhibitors

Caroline S.M. Furniss, Nigel J. Belshaw, Marcos J.C. Alcocer, Gary Williamson, Giles O. Elliott, Kurt Gebruers, Nigel P. Haigh, Neville M. Fish, Paul A. Kroon

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Steady-state kinetic approaches were used to investigate the binding of a novel Penicillium funiculosum xylanase, XYNC, with three known xylanase inhibitor proteins from wheat (Triticum aestivum). The xylanase gene (xynC) was cloned from a P. funiculosum genomic library and the deduced amino acid sequence of XYNC exhibited high sequence similarity with fungal family 11 xylanases. xynC was overexpressed in P. funiculosum and the product (XYNC: Mr=23.6 kDa; pI=3.7) purified and shown to efficiently degrade birchwood xylan [Km=0.47% w/v, Vmax=2540 μmol xylose min-1 (mg protein)-1 at pH 5.5 and 30°C] and soluble wheat arabinoxylans [Km=1.45% w/v, Vmax=7190 μmol xylose min-1 mg protein)-1 at pH 5.5 and 30°C]. The xylanase activity of XYNC was inhibited strongly by three xylanase inhibitor proteins from wheat; XIP-I, TAXI I and TAXI II. The inhibition for each was competitive, with very tight binding (Ki=3.4, 16 and 17 nM, respectively) equivalent to free energy changes (ΔG°) of -49, -45 and -45 kJ mol-1. This is the first report describing a xylanase that is inhibited by all three wheat xylanase inhibitor proteins described to date.

Original languageEnglish
Pages (from-to)24-29
Number of pages6
JournalBBA Proteins and Proteomics
Issue number1-2
Publication statusPublished - 29 Jul 2002
Externally publishedYes


  • Arabinoxylan
  • Filamentous fungus
  • Glycosyl hydrolase
  • Plant cell wall
  • Triticum aestivum

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