X-α-Man

X-α-Man (5-Bromo-4-chloro-3-indolyl α-D-mannopyranoside, CAS 125229-64-3) is a chromogenic substrate designed for specific detection of α-mannosidase (EC 3.2.1.24) activity in glycoprotein processing studies, lysosomal storage disorder diagnostics, and microbial enzyme screening. Hydrolysis by α-mannosidases cleaves the α-glycosidic linkage, releasing 5-bromo-4-chloroindoxyl, which spontaneously dimerizes and oxidizes to form an insoluble blue precipitate, enabling precise histochemical localization of enzyme activity in colonies, tissues, and cells without diffusion artifacts. This substrate distinguishes α-mannosidases from β-mannosidases (50-100x selectivity), supporting research into mannose metabolism disorders (alpha-mannosidosis), N-glycan trimming pathways, fungal mannosidase screening, and high-mannose glycoprotein analysis with optimal activity at pH 4.0-5.5.

Appearance

• White to off-white crystalline powder, odorless and mildly hygroscopic.
• Soluble in DMF (20-50 mg/mL), methanol:DMF (1:1); limited water solubility (1-3 mM).

Source

• Koenigs-Knorr glycosylation: protected α-D-mannopyranosyl bromide + 5-bromo-4-chloroindol-3-ol, silver carbonate catalysis.
• Commercial molecular biology grade from Sigma-Aldrich (B4526).

Molecular Weight and Structure

• C14H15BrClNO6, 408.63 g/mol; monoisotopic mass 406.98 Da.
• (5-Br-4-Cl-3-indolyl) α-D-Manp; α-(1→O)-glycosidic bond cleaved by α-mannosidas