Syntheses and testing of substrates and mechanism-based inactivators for xylanases.

The syntheses of the 2,5- and 3,4-dinitrophenyl beta-xylobiosides by two separate routes are described, as well as the syntheses of the 2,4-dinitrophenyl beta-glycosides of 2-chloro-2-deoxy-xylobiose and 2-deoxy-2-fluoro-xylobiose. Both the 3,4- and 2,5-dinitrophenyl beta-xylobiosides proved to be good substrates for the Bacillus subtilis xylanase, with kcat/Km values of 1.0 and 34.4 mM-1 s-1, respectively. Excellent time-dependent inactivation of the exoxylanase/glucanase from Cellulomonas fimi was provided by 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-xylobioside, according to inactivation parameters of ki = 0.057 min-1 and Ki = 0.0035 mM.