Thermomonospora fusca BD25 produces relatively high levels of activity of β-xylosidase and α-L-arabinofuranosidase. The aim of the work described in this study was to characterize some properties of β-xylosidase and α-L-arabinofuranosidase produced by T. fusca BD25 when growing on oat spelt xylan as the main carbon and energy sources. | Turk J Biol 24 (2000) 753–767 © TÜBİTAK Characterization of β-Xylosidase and α-L-Arabinofuranosidase Activities From Thermomonospora Fusca BD25 Münir TUNCER Mersin University, Faculty of Arts and Science, Department of Biology, Çiftlikköy, 33342 Mersin-TURKEY Received: Abstract: Thermomonospora fusca BD25 produces relatively high levels of activity of β-xylosidase and α-L-arabinofuranosidase. The aim of the work described in this study was to characterize some properties of β-xylosidase and α-L-arabinofuranosidase produced by T. fusca BD25 when growing on oat spelt xylan as the main carbon and energy sources. The substrates p-NPX and p-NPA reacted with β-xylosidase and α-L-arabinofuranosidase with specific activities of U mg-1 protein and U mg-1 protein, respectively. The β-xylosidase remained stable at up to 65 °C, but α-Larabinofuranosidase lost 10 % of its maximum activity at 55 °C. β-xylosidase and α-Larabinofuranosidase activities remained at 86 % and 83 % of their maximum activities after 9 h of incubation at 50 °C. The maximum relative β-xylosidase activity occurred ( U mg-1 protein) at pH with a 50 % decrease of maximum relative activity occurring at pH and 10. α-Larabinofuranosidase exhibited maximum relative activity ( U mg-1 protein) at pH with 54 % and 55 % activities remaining at pH of and 11, respectively. The apparent Km values for the crude β-xylosidase and α-L-arabinofuranosidase preparations were mM of p-NPX and mM of pNPA, while the Vmax values were µmol p-nitrophenol ml-1 min-1 and µmol p-nitrophenol ml1 min-1, respectively. The addition of D-xylose (10 mM) to the reaction mixture caused a 10 % reduction in β-xylosidase activity as the end-product inhibitor. However, a 15 % reduction in α-Larabinofuranosidase activity was detected when L-arabinose (10 mM) was added to the reaction mixture. Key Words: β-xylosidase, α-L-arabinofuranosidase, lignocellulose degradation, .
