X-GalNAc

X-GalNAc (5-Bromo-4-chloro-3-indolyl N-acetyl-β-D-galactosaminide, CAS 129572-48-1) is a chromogenic substrate optimized for detecting β-N-acetylgalactosaminidase (β-GalNAcase, EC 3.2.1.53) activity in glycobiology research, lysosomal storage disorder diagnostics, and microbial enzyme screening. Hydrolysis by β-GalNAcase cleaves the β-glycosidic bond, releasing 5-bromo-4-chloroindoxyl, which auto-oxidizes and dimerizes to form an insoluble dark blue precipitate for precise histochemical localization without product diffusion. This substrate distinguishes β-GalNAcase from β-GlcNAcase (10-100x selectivity), supporting O-glycan processing studies, mucin degradation analysis, Sanfilippo syndrome (MPS III) diagnostics, and screening of chitinase/lysozyme homologs in pathogenic bacteria, offering superior spatial resolution over soluble pNP-GalNAc chromogens with optimal activity at pH 4.0-5.0.

Appearance

• Off-white to pale yellow crystalline powder, odorless and hygroscopic.
• Soluble in DMF/DMSO (10-30 mM); limited water solubility (1-2 mM).

Source

• Koenigs-Knorr synthesis: peracetylated GalNAc-α-bromide + 5-Br-4-Cl-indol-3-ol, Ag2CO3 catalysis, selective β-deacetylation.
• Research grade from Apollo Scientific (BIB1741), biochemical suppliers.

Molecular Weight and Structure

• C16H18BrClN2O6, 449.68 g/mol; monoisotopic mass 449.9528 Da.
• 5-Br-4-Cl-3-indolyl β-D-GalNAc; β-(1→O)-N-acetylgalactosaminide linkage