title: Effective induction, purification and characterization of Trichoderma koningii G-39 beta-xylosidase with high transferase activity.
abstract: A beta-xylosidase was induced and purified from the culture filtrate of Trichoderma koningii G-39, grown in a medium containing 1% oat spelts xylan and 0.1% xylose. The presence of xylose unequivocally enhanced the induction of beta-xylosidase. The purified enzyme, which exhibited a significant alpha-arabinosidase activity, was obtained with high yield simply via ethanol precipitation and a single anion-exchange chromatography and was characterized as a monomeric glycoprotein with an estimated molecular mass of 104 kDa and a pI of 4.6. The K(m) values towards p-nitrophenyl beta-D-xylopyranoside and p-nitrophenyl alpha-L-arabinopyranoside are 0.04 and 7.5 mM, respectively. It is stable at pH 2.5-7.4, 37 degrees C. The pH and temperature optima are in the range of 3.5-4.0 and 55-60 degrees C, respectively. Contrary to most beta-xylosidases from other sources, Hg(2+) (up to 25 mM) has no effect on enzyme activity. Xylose was shown to inhibit the purified enzyme with a moderate K(i) value of 5 mM. The enzyme exhibited transxylosylation activity and was characterized as a 'retaining' enzyme, catalysing the hydrolysis of substrate with the retention of anomeric configuration.
authors.affiliation: Department of Applied Chemistry, National Chiao Tung University, Hsin-Chu,Taiwan, 30050, People's Republic of China.
authors.forename: Y K
authors.initials: YK
authors.lastname: Li
authors.forename: H J
authors.initials: HJ
authors.lastname: Yao
authors.forename: Y t
authors.initials: Yt
authors.lastname: Cho
mesh_terms: D001709:Biotechnology; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability; D007526:Isoelectric Point; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000494:pharmacology; D008970:Molecular Weight; D013379:Substrate Specificity; D013696:Temperature; D014242:Trichoderma / Q000201:enzymology*; D014995:Xylosidases / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D004791:Enzyme Inhibitors; D008670:Metals; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase