X-Gal (5-Bromo-4-Chloro-3-Indolyl β-D-Galactopyranoside)

X-Gal is a widely used chromogenic substrate for β-galactosidase. It yields a dark blue precipitate at the site of enzymatic activity. X-Gal is useful for numerous histochemical and molecular biology applications, including detection of lacZ activity in cells and tissues. In contrast to β-glucuronidase as a gene marker, β-galactosidase can be fixed in cells and tissues with glutaraldehyde without loss of activity and detected with high resolution using X-Gal.


• Chromogenic substrate
• Cell permeant
• β-galactosidase activity can still be detected using X-Gal after fixation

Additional Information About Glycosidase Enzymes
Glycosidase enzymes exhibit very high selectivity for hydrolysis of their preferred sugars. For example, β-galactosidase rapidly hydrolyzes β-D-galactopyranosides but usually does not hydrolyze either the anomeric α-D-galactopyranosides or the isomeric β-D-glucopyranosides. Endogenous glycosidase activity is frequently used to characterize strains of microorganisms and to selectively label organelles of mammalian cells; defects in glycosidase activity are characteristic of several diseases.

In addition, glycosidases are important reporter gene markers. Specifically, lacZ, which encodes β-galactosidase, is extensively used as a reporter gene in animals and yeast, whereas the β-glucuronidase (GUS) gene is a popular reporter gene in plants. Glycosidase substrates are also used in conjunction with glycosidase-conjugated secondary detection reagents in immunohistochemical techniques and enzyme-linked immunosorbent assays (ELISAs). See all of our Molecular Probes™ fluorogenic and chromogenic glycosidase substrates.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.