Magenta‑α‑Gal

Magenta‑α‑Gal (CAS 198402‑60‑7), systematically 5‑bromo‑6‑chloro‑3‑indolyl α‑D‑galactopyranoside, is a synthetic α‑D‑galactosidase‑specific chromogenic substrate in which a 5‑bromo‑6‑chloro‑3‑indoxyl aglycone is linked via an α‑glycosidic bond to D‑galactose. When hydrolyzed by α‑D‑galactosidase or α‑galactoside‑cleaving enzymes, the indoxyl moiety is released and undergoes aerial oxidation, forming an insoluble magenta‑colored indigo‑type precipitate that enables visual detection of enzyme activity. This substrate is commonly incorporated into selective agar media to screen and differentiate α‑galactosidase‑producing microorganisms, such as specific yeast and bacterial species, as well as in enzyme‑kinetic assays for purified or recombinant α‑D‑galactosidases. The distinct magenta color provides good contrast against background pigmentation, making it useful for phenotypic screening in mixed‑culture systems. Compared with fluorogenic or other colorimetric α‑galactosidase substrates, Magenta‑α‑Gal is optimized for chromogenic, solid‑medium applications and is compatible with standard laboratory buffers and microbial‑culture matrices.

Appearance

• Off‑white to pale yellow crystalline powder or lyophilized solid.
• Fine, free‑flowing texture suitable for accurate weighing and dissolution in aqueous or mixed solvents.

Source / synthesis

• Synthetically produced by coupling 5‑bromo‑6‑chloro‑3‑indoxyl with α‑D‑galactose under glycosylation conditions to form the α‑D‑galactopyranoside derivative.
• Commercially manufactured by specialty enzyme‑substrate and biochemical suppliers as a research‑grade reagent (e.g., Glentham, GoldBio‑style vendors).

Molecular weight and structure

• Molecular formula: C14H15BrClNO6\text{C}_{14}\text{H}_{15}\text{BrClNO}_{6}C14H15BrClNO6.
• Molecular weight: 408.60–408.63 g/mol.
• Structure: 5‑bromo‑6‑chloro‑1H‑indol‑3‑yl α‑D‑galactopyranoside, with an α‑glycosidic linkage between the indole C3‑O and the D‑galactose ring in the (2R,3R,4S,5R,6R) configuration.

Sugar specificity

• Specifically hydrolyzed by α‑D‑galactosidases (EC 3.2.1.22) and other α‑galactoside‑cleaving enzymes.
• Shows minimal cross‑reactivity with β‑glycosidases and other α‑glycosidases (e.g., α‑glucosidase, α‑fucosidase) under optimized assay conditions.

Biological activity

• Acts as a chromogenic reporter for α‑D‑galactosidase‑mediated hydrolysis of terminal α‑D‑galactosyl linkages in glycoproteins, glycolipids, and oligosaccharides.
• Enzymatic cleavage yields 5‑bromo‑6‑chloro‑3‑indoxyl, which oxidizes and dimerizes into a magenta‑colored, water‑insoluble pigment, providing a sensitive, low‑background readout in solid‑medium and solution‑based assays.

Purity and microbial contamination

• Typically supplied at ≥98% purity as determined by HPLC or equivalent analytical methods.
• Certificates of analysis from commercial vendors usually confirm acceptable levels of residual solvents, heavy metals, and non‑sterile, low‑microbial‑contamination status suitable for microbiological and biochemical use.

Identity and quality control

• Identity verified by NMR, HPLC, MS, and elemental analysis, with batch‑specific certificates of analysis provided by manufacturers.
• Quality‑control checks generally include appearance, solubility, UV/Vis spectral characteristics, and performance in a defined α‑D‑galactosidase activity assay system.

Shelf life and storage

• Shelf life is typically 12–24 months when stored as a dry powder at –20 °C in a tightly sealed container, protected from moisture and light.
• Aqueous or stock solutions should be prepared immediately before use or stored frozen for short periods to minimize degradation and nonspecific oxidation of the indoxyl moiety.

Application

• Screening and phenotypic differentiation of α‑D‑galactosidase‑producing microbes (e.g., yeasts and some bacteria) on selective agar media.
• Enzyme‑activity assays for recombinant or purified α‑D‑galactosidases in solution or immobilized formats.
• Histochemical or cytochemical localization of α‑D‑galactosidase activity in tissue sections and cell preparations.

Key characteristics

• High sensitivity and low background due to formation of an insoluble magenta‑colored dye upon α‑D‑galactosidase hydrolysis.
• Defined α‑D‑galactopyranoside linkage providing selectivity for α‑D‑galactosidases over other glycosidases.
• Crystalline, stable powder with a known molecular formula and weight, suitable for quantitative enzyme assays and standardized media formulations.

citation

• GoldBio – 5‑Bromo‑6‑chloro‑3‑indoxyl‑α‑D‑galactopyranoside substrate page: https://www.goldbio.com/products/5-bromo-6-chloro-3-indoxyl-alpha-d-galactopyranoside
• GuideChem – 5‑bromo‑6‑chloro‑3‑indoxyl‑α‑D‑galactopyranoside data entry (CAS 198402‑60‑7): https://wap.guidechem.com/encyclopedia/5-bromo-6-chloro-3-indoxyl-alp-dic199033.html
• Glentham – 5‑Bromo‑6‑chloro‑3‑indoxyl‑α‑D‑galactopyranoside (Magenta‑α‑Gal) product entry: https://www.glentham.com/en/products/product/GC9885/
• GoldBio‑type enzyme‑substrate catalog (α‑galactosidase substrates overview): https://www.goldbio.com/products/5-bromo-6-chloro-3-indoxyl-alpha-d-galactopyranoside
• Glentham product‑specific page (Molecular formula MF C14H15BrClNO6, MW 408.60): https://www.glentham.com/en/products/product/GC9885/
• α‑Gal‑epitope biology review (background on α‑galactosidase‑related epitopes): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8974695/
• Immunity‑to‑α‑Gal review (context for α‑galactosidase‑related systems): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5704288/
• MedChemExpress – α‑galactosidase‑substrate catalog (for assay‑format and application reference): https://www.medchemexpress.com/+%C2%A6-galactosidase.html
• abcam – MU‑alpha‑GAL fluorigenic α‑D‑galactosidase substrate (for enzyme‑substrate concept context): https://www.abcam.com/en-us/products/biochemicals/mu-alpha-gal-fluorogenic-alpha-d-galactosidase-substrate-ab146357
• General enzyme‑substrate resource (chromogenic and fluorogenic glycosidase substrates): https://www.medchemexpress.com/ (α‑galactosidase‑substrate section)