title: A kinetic study on pH-activity relationship of XynA from alkaliphilic Bacillus halodurans C-125 using aryl-xylobiosides.
abstract: Xylanase A from alkaliphilic Bacillus halodurans C-125 was expressed in Escherichia coli and purified by affinity and anion exchange chromatographies. It exhibited a strong substrate inhibition using xylan as the substrate. Its K(i) value increased with an increase in pH. The effect of pH on the enzyme activity was determined using two aryl-xylobiosides as substrates, and it was found that the enzyme had a flat k(cat)-pH curve in the pH range of 5.8-8.8. This range was different from that obtained with 0.45% xylan as previously reported (Honda, H. et al., Agric. Biol. Chem., 49, 3165-3169, 1985). The substrate inhibition was presumed to cause the difference. It has been clarified that the use of aryl-xylobiosides as substrates yields more accurate kinetic results than that of xylan.
authors.affiliation: Enzyme Laboratory, National Food Research Institute, Kannondai, Ibaraki 305-8642, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Nishimoto
authors.forename: Yuji
authors.initials: Y
authors.lastname: Honda
authors.forename: Motomitsu
authors.initials: M
authors.lastname: Kitaoka
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Hayashi