Syntheses of 4-Methylumbelliferyl-β-D-Xylobioside and 5-Bromo-3-Indolyl-β-D-Xylobioside for Sensitive Detection of Xylanase Activity on Agar Plates

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  4-Methylumbelliferyl-β-D-xylobioside (MU-X₂) and 5-bromo-3-indolyl-β-D-xylobioside (BI-X₂) were synthesized as substrates for the detection of xylanase activity on agar plates. A family F/10 xylanase from Streptomyces olivaceoviridis E-86 (FXYN) was able to be more sensitively detected than RBB-xylan by using MU-X₂ as a substrate. A mutant xylanase E128H/FXYN having only 1/1000 of the activity of FXYN was also able to be detected on the MU-X₂ plate but was not detected on the RBB-xylan plate. A family G/11 xylanase from Streptomyces lividans 66 (Xyn B) was not detected on the MU-X₂ plate, but it was able to be detected on the RBB-xylan plate, suggesting that the MU-X₂ substrate is specific to family F/10 xylanases. However, none of the xylanases were detected effectively by using BI-X₂ as a substrate.