Comparative study of xylanase kinetics using dinitrosalicylic, arsenomolybdate, and ion chromatographic assays

Xylanases are commonly assayed by the dinitrosalicylic acid (DNS) or the arsenomolybdate (ARS) method. However, specific activities are many times higher with DNS than with ARS. This is because the DNS assay is more reactive and the ARS assay is less reactive with xylooligosaccharides than with xylose. Xylose is often used as a standard, even though oligosaccharides are prevalent, so the DNS method overestimates and the ARS method underestimates specific activity. Ion chromatography, with pulsed amperometric detection, separates and measures all products and intermediates, but quantitation on a molar basis is difficult, because few xylooligosaccharide response factors are known. This report directly compares these three assay methods for the assay of xylanase activities.