p-Nitrophenyl β-Glycosides of β-1,4-Gluco/xylo-disaccharides for the Characterization of Subsites in Endo-xylanases

To investigate the substrate recognition at the minus subsites of glycoside hydrolase family 10 xylanases, the kinetic parameters of four xylanases on all four p-nitrophenyl β-glycosides of β-1,4-gluco/xylo-disaccharides were determined. All four xylanases hydrolyzed all the four substrates examined. The Km values of all the enzymes on the four substrates lined up in the same order, indicating that both the subsites -1 and -2 of all the enzymes prefer xylose to glucose. The comparison of the parameters on the substrates gave detailed information on the substrate recognition at each subsite -1 and -2.