Purification and characterization of a new xylanase from Acrophialophora nainiana

A new xylanase activity (XynII) was isolated from liquid state cultures of Acrophialophora nainiana containing birchwood xylan as carbon source. XynII was purified to apparent homogeneity by gel filtration and ion exchange ch romatographies. The enzyme was optimally active at 55 degrees C and pH 7.0. XynII had molecular mass of 22 630 +/- 3.0 and 22 165 Da, as determined by mass spectrometry and SDS-PAGE, respectively. The purified enzyme was able to act only on xylan as substrate. The apparent K-m values on soluble and insoluble birchwood xylans were 40.9 and 16.1 mg ml(-1), respectively. The enzyme showed good thermal stability with half lives of 44 h at 55 degrees C and ca. 1 h at 60 degrees C The N-terminal sequence of XynII showed homol ogy with a xylanase grouped in family G/11. The enzyme did not show amino a cid composition similarity with xylanases from some fungi and Bacillus amyl oliquefaciens. (C) 2000 Elsevier Science B.V. All rights reserved.