XYLT2 Human
Description
Definition and Basic Characteristics
XYLT2 (Xylosyltransferase 2) is a glycosyltransferase enzyme encoded by the XYLT2 gene located on human chromosome 17 (OMIM: 608125). It catalyzes the transfer of xylose from UDP-xylose to serine residues in core proteins, initiating glycosaminoglycan (GAG) chain biosynthesis for proteoglycans like chondroitin sulfate, heparan sulfate, and dermatan sulfate .
Table 1: Key Properties of XYLT2
| Property | Description |
|---|---|
| Gene Location | 17q21.3–q22 (human) |
| Protein Length | 865 amino acids |
| Molecular Mass | ~94 kDa (glycosylated) |
| Expression Sites | Ubiquitous; prominent in liver, kidney, platelets, and ER/Golgi |
Functional Mechanism and Enzymatic Role
XYLT2 operates in the endoplasmic reticulum (ER) and Golgi apparatus, where it adds xylose to serine residues of core proteins. This step is critical for proteoglycan assembly, which regulates extracellular matrix (ECM) integrity, cell signaling, and morphogen gradients .
Key Functional Aspects:
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Substrate Specificity: Prefers UDP-xylose over other nucleotide donors .
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Isoform Dominance: Predominant in serum compared to XYLT1 due to higher substrate affinity (Kₘ ≈ 2.5 μM vs. 22 μM for XYLT1) .
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Cellular Sources:
Clinical and Pathological Associations
XYLT2 is implicated in multiple diseases, including genetic disorders and organ dysfunctions:
Table 2: Diseases Linked to XYLT2 Dysregulation
SOS: Autosomal recessive disorder caused by XYLT2 truncations (e.g., novel homozygous variant c.912delA in exon 8) . Early manifestations include prenatal nuchal translucency and postnatal skeletal dysplasia .
Serum Dynamics
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Platelet Contribution: In vitro clotting releases platelet-derived XYLT2, explaining elevated serum levels .
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Liver Dependency: XYLT2 knockout mice show 99% reduction in serum activity, confirming hepatic origin .
Organ Pathology in Knockout Models
Table 3: XYLT2 Knockout Phenotypes
| Organ System | Wild-Type (Control) | XYLT2−/− Mice |
|---|---|---|
| Liver | Normal ECM, no cysts | Biliary epithelial hyperplasia, fibrosis, cysts |
| Kidney | Functional tubules | Tubular dilation, β-catenin accumulation, cysts |
Mechanistic Insights:
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Cyst Formation: Reduced proteoglycans disrupt cell-matrix interactions, promoting epithelial hyperplasia and cyst expansion .
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β-Catenin Signaling: Elevated β-catenin in cystic epithelia suggests Wnt pathway dysregulation .
Tissue Expression and Localization
XYLT2 is expressed in diverse tissues, with notable activity in:
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Liver: Primary source of circulating enzyme; critical for hepatocellular proteoglycan biosynthesis .
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Kidney: Contributes to renal tubule integrity; deficiency leads to fibrosis and cysts .
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Platelets: Stored in α-granules; released during coagulation .
Table 4: XYLT2 Tissue Expression (Human Protein Atlas)
| Tissue | Expression Level | Key Proteoglycans Affected |
|---|---|---|
| Liver | High | Decorin, Syndecans, Glypicans |
| Kidney | Moderate | Heparan sulfate proteoglycans (HSPGs) |
| Skin | Low | Dermatan sulfate, Chondroitin sulfate |
Therapeutic Implications
Product Specs
Xylosyltransferase 2 (XYLT2) is an enzyme found throughout the body and belongs to the glycosyltransferases family. XYLT2 plays a crucial role in the formation of proteoglycans by attaching GAG chains to a protein. It achieves this by transferring a xylose molecule from a donor molecule (nucleoside diphosphate) to serine residues on the protein. XYLT2 is located in the ER and the cis Golgi, and is also found in the extracellular matrix.
Recombinant Human XYLT2 is a single, glycosylated polypeptide chain. It consists of 839 amino acids (Gly37-Arg865, luminal domain, isoform 1, natural variant with Thr305) and has a molecular weight of 94.0kDa. This protein includes a N-terminal linker (2 additional amino acids), a C-terminal linker (2 additional amino acids), and a C-terminal His-tag (6 additional amino acids).
XYLT2 is filtered (0.4 µm) and lyophilized in a solution of 0.05 M PBS and 0.075 M NaCl, at pH 7.4.
To create a working stock solution, it is recommended to add deionized water to the lyophilized pellet until it reaches a concentration of about 0.5mg/ml. Allow the pellet to dissolve completely. Please note that XYLT2 is not sterile. Before using it in cell culture, it is crucial to filter the product using an appropriate sterile filter.
The purity is determined to be greater than 95.0% using SDS-PAGE analysis.
Xylosyltransferase 2, Peptide O-xylosyltransferase 1, Xylosyltransferase II, XT-II, XylT-II, XYLT2, XT2.
HEK293 Cells.
ASGLEEDEAG EKGRQRKPRP LDPGEGSKDT DSSAGRRGST GRRHGRWRGR AESPGVPVAK VVRAVTSRQR ASRRVPPAPP PEAPGRQNLS GAAAGEALVG AAGFPPHGDT GSVEGAPQPT DNGFTPKCEI VGKDALSALA RASTKQCQQE IANVVCLHQA GSLMPKAVPR HCQLTGKMSP GIQWDESQAQ QPMDGPPVRI AYMLVVHGRA IRQLKRLLKA VYHEQHFFYI HVDKRSDYLH REVVELAQGY DNVRVTPWRM VTIWGGASLL TMYLRSMRDL LEVPGWAWDF FINLSATDYP TRTNEELVAF LSKNRDKNFL KSHGRDNSRF IKKQGLDRLF HECDSHMWRL GERQIPAGIV VDGGSDWFVL TRSFVEYVVY TDDPLVAQLR QFYTYTLLPA ESFFHTVLEN SLACETLVDN NLRVTNWNRK LGCKCQYKHI VDWCGCSPND FKPQDFLRLQ QVSRPTFFAR KFESTVNQEV LEILDFHLYG SYPPGTPALK AYWENTYDAA DGPSGLSDVM LTAYTAFARL SLHHAATAAP PMGTPLCRFE PRGLPSSVHL YFYDDHFQGY LVTQAVQPSA QGPAETLEMW LMPQGSLKLL GRSDQASRLQ SLEVGTDWDP KERLFRNFGG LLGPLDEPVA VQRWARGPNL TATVVWIDPT YVVATSYDIT VDTETEVTQY KPPLSRPLRP GPWTVRLLQF WEPLGETRFL VLPLTFNRKL PLRKDDASWL HAGPPHNEYM EQSFQGLSSI LNLPQPELAE EAAQRHTQLT GPALEAWTDR ELSSFWSVAG LCAIGPSPCP SLEPCRLTSW SSLSPDPKSE LGPVKADGRL RKLHHHHHH.
Product Science Overview
Xylosyltransferase 2 (XylT2) is an enzyme that plays a crucial role in the biosynthesis of glycosaminoglycans (GAGs), which are essential components of proteoglycans. Proteoglycans are vital for various biological processes, including cell signaling, morphogenesis, and maintaining the structural integrity of tissues .
XylT2 is one of the two isoenzymes of xylosyltransferase, the other being Xylosyltransferase 1 (XylT1). Both enzymes catalyze the initial and rate-limiting step in the assembly of GAG chains by transferring xylose from UDP-xylose to specific serine residues on core proteins . This step is critical for the subsequent elongation of the tetrasaccharide linkage region, which leads to the polymerization of chondroitin sulfate, heparan sulfate, dermatan sulfate, and heparin .
XylT2 is predominantly found in the endoplasmic reticulum and cis-Golgi of cells, where it performs its enzymatic functions . It is also present in the serum, where it can serve as a biomarker for various diseases. The liver is a significant source of serum XylT2 activity, and platelets also contribute to its levels in the blood .
Altered serum XylT2 activity has been proposed as a biomarker for diseases that affect proteoglycan metabolism, such as diabetes and systemic sclerosis . Increased fibrosis and accumulation of extracellular matrix components, including proteoglycans, are common in these conditions, leading to speculation that elevated serum XylT2 activity indicates increased proteoglycan biosynthesis .
Recombinant human XylT2 has been cloned and expressed for research purposes. This recombinant protein is enzymatically active and can catalyze the initial steps in GAG biosynthesis . The availability of recombinant XylT2 allows for detailed studies on its function and potential therapeutic applications.
