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Biochim Biophys Acta. 2004 Sep 1;1701(1-2):121-8.

The inhibition specificity of recombinant Penicillium funiculosum xylanase B towards wheat proteinaceous inhibitors.

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Laboratoire de Biochimie et Biologie de la Nutrition, Institut Méditerranéen de Recherche en Nutrition, UMR Université Aix Marseille III-INRA 1111, Service 342, Faculté des Sciences et Techniques Saint-Jérôme, 13397 Marseille Cedex 20, France.


The filamentous fungus Penicillium funiculosum produces a mixture of modular and non-modular xylanases belonging to different glycoside hydrolase (GH) families. In the present study, we heterologously expressed the cDNA encoding GH11 xylanase B (XYNB) and studied the enzymatic properties of the recombinant enzyme. Expression in Escherichia coli led to the partial purification of a glutathione fusion protein from the soluble fraction whereas the recombinant protein produced in Pichia pastoris was successfully purified using a one-step chromatography. Despite O-glycosylation heterogeneity, the purified enzyme efficiently degraded low viscosity xylan [K(m)=40+/-3 g l(-1), V(max)=16.1+/-0.8 micromol xylose min(-1) and k(cat)=5405+/-150 s(-1) at pH 4.2 and 45 degrees C] and medium viscosity xylan [K(m)=34.5+/-3.2 g l(-1), V(max)=14.9+/-1.0 micromol xylose min(-1)k(cat)=4966+/-333 s(-1) at pH 4.2 and 45 degrees C]. XYNB was further tested for its ability to interact with wheat xylanase inhibitors. The xylanase activity of XYNB produced in P. pastoris was strongly inhibited by both XIP-I and TAXI-I in a competitive manner, with a K(i) of 89.7+/-8.5 and 2.9+/-0.3 nM, respectively, whereas no inhibition was detected with TAXI-II. Physical interaction of both TAXI-I and XIP-I with XYNB was observed using titration curves across a pH range 3-9.

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