FEMS Microbiology Letters 118 (1994) 305-310 © 1994 Federation of European Microbiological Societies 0378-1097/94/$07.00 Published by Elsevier 305 FEMSLE 05955 Purification and characterization of an extracellular endo-l,4-/3-xylanase from Fusarium oxysporum f. sp. melonis T.M. Alconada a and M.J. Martlnez ,,b a Departamento de Ciencias Biol6gicas, Facultad de Ciencias Exactas y Naturales, 2 ° Pabelldn, Ciudad Universitaria, 1428 Buenos Aires, Argentina, and b Centro de Investigaciones Bioldgicas (CSIC), Departamento de Microbiolog{a Molecular, Veldzquez 144, 28006 Madrid, Spain (Received 18 February 1994; revision received and accepted 11 March 1994) Abstract: Fusarium oxysporum f. sp. melonis produces extracellular endo-l,4-/3-xylanase and /3-xylosidase when grown in shaken culture at 26°C in a mineral salts medium containing oat spelt xylan and glucose as carbon sources. Endo-l,4-/3-xylanase was purified 251 times from 5-day-old culture filtrates, by Sephacryl S-200, ion exchange and gel filtration HPLC. The purified sample yielded a single band in SDS polyacrylamide gels with a molecular mass of 80 kDa on electrophoretic mobility and 83 kDa by gel filtration behavior. High activity of the endo-l,4-/3-xylanase against xylan was observed between 5 and 8 pH, and between 40 and 60°C, the optimum pH and temperature being 5.0 and 50°C, respectively. Kinetic properties of the enzyme are similar to those of other fungal xylanases, showing high affinity towards oat spelt xylan with a K m of 1 mM expressed as xylose equivalent. Key words: Fusarium oxysporum f. sp. melon&; Endo-l,4-/3-xylanase activity;/3-Xylosidase activity Introduction D-Xylans are the major components found in the hemicellulosic fraction in the cell walls of higher plants [1], particularly in the primary cell walls of monocotyledonous plants [2]. Natural xylans are heterogeneous polysaccharides Consist- ing of a backbone chain of /3-1,4-1inked D- xylopyranosyl residues and side chains of differ- ent substituents [3,4]. The complete hydrolysis of xylans requires the action of several enzymes, * Corresponding author. Fax: (0341) 5627518. probably analogous to the synergistic enzyme ac- tion involved in crystalline cellulose degradation [7]. Endoxylanases randomly cleave the fl-l,4- bonds in the polyxylose backbone, yielding oligosaccharides of varied chain lengths. /3- Xylosidase activity generates i>xylose from both short chain oligosaccharides and xylobiose [4,5]. The action of exoxylanases is less frequent [7], although it is not clear whether this exoenzyme is a separate entity from the/3-xylosidase [3,8]. Since a number of microorganisms pathogenic to plants are known to produce xylanases, the study of these enzymes to evaluate their possible role in pathogenesis is of great interest [2,9]. SSDI 0378-1097(94)00101-V Downloaded from https://academic.oup.com/femsle/article/118/3/305/541106 by guest on 09 September 2023