X‑β‑Xyl

X‑β‑Xyl (CAS 207606‑55‑1) is a synthetic β‑D‑xylosidase‑specific chromogenic substrate in which 5‑bromo‑4‑chloro‑3‑indoxyl is linked via a β‑glycosidic bond to D‑xylose. When hydrolyzed by β‑D‑xylosidase (EC 3.2.1.37) or related xylo‑oligosaccharide‑cleaving enzymes, the indoxyl moiety is released and undergoes aerial oxidation to form an insoluble blue–violet indigo‑type dye, enabling visual or spectrophotometric detection of enzyme activity. This substrate is commonly used in selective agar media to screen xylose‑utilizing microorganisms, in enzyme‑kinetic assays for recombinant or purified β‑D‑xylosidases, and in histochemical staining for spatial localization of β‑D‑xylosidase activity in tissue or cell preparations. Compared with other X‑type xylosides, X‑β‑Xyl offers good sensitivity and low background, making it suitable for both qualitative and semi‑quantitative applications in standard laboratory buffers and media.

Appearance

• White to off‑white 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‑4‑chloro‑3‑indoxyl with β‑D‑xylose under glycosylation conditions to form the β‑D‑xylopyranoside.
• Commercially manufactured by specialty carbohydrate and enzyme‑substrate suppliers as a high‑purity, research‑use‑only reagent.

Molecular weight and structure

• Molecular formula: C13H13BrClNO5C13​H13​BrClNO5​.
• Molecular weight: 378.60–378.61 g/mol.
• Structure: 5‑bromo‑4‑chloro‑1H‑indol‑3‑yl β‑D‑xylopyranoside, with a β‑(1→?) glycosidic linkage between the indole C3‑O and the D‑xylose ring.

Sugar specificity

• Specifically hydrolyzed by β‑D‑xylosidases (EC 3.2.1.37) and closely related β‑D‑xyloside‑cleaving enzymes.
• Shows minimal cross‑reactivity with other β‑glycosidases (e.g., β‑glucosidase, β‑galactosidase) when used under optimized assay conditions.

Biological activity

• Acts as a chromogenic reporter for β‑D‑xylosidase‑mediated hydrolysis of β‑D‑xylosyl linkages in xylo‑oligosaccharides, xylans, and xyloglycosides.
• Enzymatic cleavage yields 5‑bromo‑4‑chloro‑3‑indoxyl, which oxidizes and dimerizes into a blue–violet, water‑insoluble pigment, providing a sensitive, low‑background signal for solution‑based, gel‑based, and solid‑medium assays.

Purity and microbial contamination

• Typically supplied at ≥98–99% purity as determined by HPLC or equivalent analytical methods.
• Certificates of analysis generally confirm low levels of residual solvents, heavy metals, and absence of significant microbial contamination when stored and handled under aseptic conditions.

Identity and quality control

• Identity confirmed by NMR, HPLC, MS, and elemental analysis, with batch‑specific certificates of analysis provided by major suppliers.
• Quality‑control procedures include checks for appearance, solubility, UV/Vis spectral characteristics, and performance in a defined β‑D‑xylosidase activity assay.

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 working 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 enumeration of β‑D‑xylosidase‑producing microorganisms on selective agar media.
• Enzyme‑activity assays for recombinant or purified β‑D‑xylosidases in solution or immobilized formats.
• Histochemical or cytochemical localization of β‑D‑xylosidase activity in tissue sections or cell preparations.

Key characteristics

• High sensitivity and low background due to formation of an insoluble blue–violet dye upon β‑D‑xylosidase hydrolysis.
• Defined β‑D‑xylopyranoside linkage providing selectivity for β‑D‑xylosidases over other glycosidases.
• Crystalline, stable powder with a well‑defined molecular weight and formula suitable for quantitative enzyme assays and standardized media formulations.

citation

• ChemicalBook – 5‑Bromo‑4‑chloro‑3‑indoxyl‑β‑D‑xylopyranoside: https://www.chemicalbook.com/ChemicalProductProperty_EN_CB7450888.htm
• ChemicalBook India – β‑D‑xylopyranoside product page: https://amp.chemicalbook.com/ChemicalProductProperty_EN_CB7450888.htm?N=India
• Hepattack – X‑β‑Xyl product page: https://hepattack.com/en/product03_cid_212_pid_498.html
• Angene Scientific – 5‑Bromo‑4‑chloro‑3‑indolyl β‑D‑xylopyranoside: https://www.angenesci.com/productshow/AG002J5U.html
• GoldBio – 5‑Bromo‑4‑chloro‑3‑indoxyl‑β‑D‑xylopyranoside product entry: https://www.goldbio.com/products/5-bromo-4-chloro-3-indoxyl-beta-d-xylopyranoside
• Biosynth – 5‑Bromo‑4‑chloro‑3‑indolyl β‑D‑xylopyranoside product page: https://www.biosynth.com/p/EB03248/207606-55-1-5-bromo-4-chloro-3-indolyl-v-d-xylop
• Apollo Scientific – 5‑Bromo‑4‑chloro‑3‑indolyl β‑D‑xylopyranoside (CAS 207606‑55‑1) data sheet: https://www.sigmaaldrich.com/US/en/product/apolloscientificltd/apo456787883
• PubChem – related 5‑bromo‑4‑chloro‑3‑indolyl glycosides (for dye‑chemistry reference): https://pubchem.ncbi.nlm.nih.gov/compound/5-Bromo-4-chloro-3-indolyl-beta-D-glucopyranoside
• TCICHemicals – enzyme‑substrate catalog (for X‑type substrate‑handling guidance): https://www.tcichemicals.com/IN/en/p/B5393
• GoldBio‑style enzyme‑substrate overview (for general X‑substrate usage): https://www.goldbio.com/products/5-bromo-4-chloro-3-indoxyl-beta-d-xylopyranoside