X‑α‑Xyl (CAS 1301706‑83‑1) is a synthetic α‑D‑xylosidase‑specific chromogenic substrate in which a 5‑bromo‑4‑chloro‑3‑indolyl aglycone is linked via an α‑glycosidic bond to α‑D‑xylopyranose. When hydrolyzed by α‑D‑xylosidases (e.g., GH‑31‑type enzymes from fungi or plants), the glycosidic bond is cleaved to release the indole derivative and α‑D‑xylose; the indole then undergoes air oxidation to form a strongly colored magenta‑ or blue‑colored precipitate or dye at the site of enzyme activity. This reaction makes X‑α‑Xyl especially useful for histochemical staining of α‑D‑xylosidase activity in cells, tissues, and microbial colonies, as well as for high‑throughput screening of enzyme‑expressing clones or recombinant α‑xylosidases. The compound is typically supplied as a high‑purity, lyophilized or crystalline solid, and is compatible with standard aqueous or buffer‑based incubation systems. X‑α‑Xyl is widely used in glycobiology, plant‑cell‑wall and biomass‑research, and microbiology to visualize α‑D‑xylosidase‑dependent cleavage of xyloglucans and other xylan‑related glycoconjugates, including studies of α‑xylosidases involved in xyloglucan remodeling and biofuel‑relevant biomass deconstruction.
- Off‑white to pale yellow crystalline or lyophilized powder.
- Forms a pale yellow to colorless solution in aqueous buffer; develops a magenta‑ or blue‑colored precipitate only after enzymatic hydrolysis and oxidation of the indole‑type chromophore.
- Synthetically prepared by glycosylation of 5‑bromo‑4‑chloro‑3‑indole with α‑D‑xylopyranose or a protected α‑D‑xylsyl derivative, followed by deprotection and crystallization from aqueous or mixed‑solvent systems.
- Commercially supplied by glycobiology‑and‑enzyme‑substrate manufacturers (e.g., Hepattack, Shenzhen‑based vendors such as GeneSeqTools) as a high‑purity, research‑grade α‑xylosidase substrate.
Molecular weight and structure
- Molecular formula: C13H13BrClNO5C13H13BrClNO5.
- Molecular weight: 378.60 g/mol.
- Structure: 5‑bromo‑4‑chloro‑3‑indol‑α‑D‑xylopyranoside, with an α‑glycosidic linkage between the indole‑type aglycone and the anomeric carbon of α‑D‑xylopyranose (IUPAC: (2R,3R,4S,5R)‑2‑[(5‑bromo‑4‑chloro‑1H‑indol‑3‑yl)oxy]oxane‑3,4,5‑triol).
- Specifically hydrolyzed by α‑D‑xylosidases that cleave α‑linked D‑xylose residues from xyloglucans and other xylan‑related glycoconjugates.
- Frequently used in chromogenic panels and histochemical assays to distinguish α‑D‑xylosidase activity from other glycosidases in microbial, plant, and fungal systems.
- Serves as a chromogenic reporter whose rate of indole‑derivative release under defined pH and temperature conditions reflects α‑D‑xylosidase activity.
- Enables localization and relative quantification of α‑D‑xylosidase activity in tissue sections, cell cultures, and microbial colonies, supporting studies on plant‑cell‑wall‑xyloglucan processing and biomass‑degradation pathways.
Purity and microbial contamination
- Typically described as a “high‑purity raw material” suitable for scientific research, with purity often specified ≥95% by HPLC‑type methods by suppliers.
- Described as a non‑sterile, research‑grade solid, intended for use under standard clean‑laboratory or sterile‑handling conditions depending on the assay (e.g., histochemistry vs. colony‑screening).
Identity and quality control
- Identity based on CAS 1301706‑83‑1, molecular formula C13H13BrClNO5C13H13BrClNO5, and molecular weight 378.60 g/mol, with the systematic name 5‑bromo‑4‑chloro‑3‑indol‑α‑D‑xylopyranoside.
- Quality‑control generally includes checks for appearance, solubility, spectral properties, and performance in a defined α‑D‑xylosidase assay (e.g., histochemical or colony‑based xylosidase screens).
- Shelf life is typically 12–24 months when stored at −20 °C in a tightly sealed, light‑protected container, as the indole‑type chromophore is sensitive to light and oxidation.
- Aqueous working solutions are best prepared fresh or used immediately, as prolonged storage or air‑exposure can cause premature color development or background staining.
- Histochemical and chromogenic staining of α‑D‑xylosidase activity in tissue sections, cell cultures, and microbial colonies.
- Screening of α‑D‑xylosidase‑expressing clones in recombinant enzyme‑expression or mutagenesis studies.
- Use in plant‑biology, biomass‑and‑biofuel‑research, and glycobiology to visualize α‑D‑xylosidase‑dependent processing of xyloglucans and other xylan‑related glycoconjugates.
- Chromogenic readout: release of an indole derivative that oxidizes to a magenta‑ or blue‑colored precipitate, enabling easy visual detection of α‑D‑xylosidase activity.
- Defined α‑D‑xylopyranoside linkage providing selectivity for α‑D‑xylosidases over many other glycosidases.
- High‑purity, lyophilized solid with a known molecular formula and weight, suitable for histochemical, colony‑, and microplate‑based assays.
- Hepattack – X‑α‑Xyl product page (CAS 1301706‑83‑1, MF C₁₃H₁₃BrClNO₅, MW 378.60, high‑purity raw material): https://www.hepattack.com/en/product03_cid_212_pid_499.html
- ChemRadar – X‑Alpha‑d‑xyl database entry (CAS 1301706‑83‑1, IUPAC name, MF C₁₃H₁₃BrClNO₅, MW 378.60): https://www.chemradar.com/en/tools/cas/detail/087y6ifaq1?cas=1301706-83-1
- GeneSeqTools – X‑α‑Xyl listing in product catalog (CAS 1301706‑83‑1, within X‑glycoside chromogen series): http://geneseqtools.com/en/product02_cid_212.html
- Mini‑review or structural paper on α‑xylosidase (e.g., Aspergillus niger AxlA, GH‑31 α‑xylosidase): https://pubs.acs.org/doi/10.1021/acssuschemeng.9b07073
- Biochemical characterization of secreted α‑xylosidase (AxlA from fungal systems): https://pmc.ncbi.nlm.nih.gov/articles/PMC3234869/
- Xyloside‑overview article (context on chromogenic and priming‑type xylosides): https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/xyloside
- X‑β‑Xyl (β‑D‑xylosidase substrate, analogous indolyl‑xyloside) PubChem entry (for method‑context comparison): https://pubchem.ncbi.nlm.nih.gov/compound/207606-55-1
- Xylogalacturonan hydrolase paper (for general glycosidase‑substrate‑context): https://pmc.ncbi.nlm.nih.gov/articles/PMC1135002/
- General glycosidase‑substrate catalog (X‑α‑Xyl and related indolyl‑xyl‑glycosides overview): https://www.chemicalbook.com/ (search for “1301706‑83‑1”).
- Xylose‑glycobiology overview (background on α‑D‑xylosidase‑substrate structures): https://en.wikipedia.org/wiki/Fucose (supplement with xylose‑specific reviews via PubMed search for “α‑xylosidase substrate specificity”).
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