B4GALT7

Xylosylprotein beta 1,4-galactosyltransferase, polypeptide 7 (galactosyltransferase I)
Identifiers
Symbols	B4GALT7; XGALT1; XGPT1
External IDs	OMIM: 604327 MGI: 2384987 HomoloGene: 5248 GeneCards: B4GALT7 Gene
EC number	2.4.1.133
Gene Ontology Molecular function • galactosyltransferase activity • galactosyltransferase activity • transferase activity, transferring glycosyl groups • xylosylprotein 4-beta-galactosyltransferase activity • metal ion binding Cellular component • Golgi apparatus • membrane • integral to membrane • Golgi cisterna membrane Biological process • carbohydrate metabolic process • glycosaminoglycan biosynthetic process • proteoglycan metabolic process • protein modification process • fibril organization • negative regulation of fibroblast proliferation Sources: Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	11285	218271
Ensembl	ENSG00000027847	ENSMUSG00000021504
UniProt	Q9UBV7	Q3TAW1
RefSeq (mRNA)	NM_007255	NM_146045.1
RefSeq (protein)	NP_009186	NP_666157.1
Location (UCSC)	Chr 5: 177.03 – 177.04 Mb	Chr 13: 55.7 – 55.71 Mb
PubMed search	[1]	[2]

Beta-1,4-galactosyltransferase 7 also known as galactosyltransferase I is an enzyme that in humans is encoded by the B4GALT7 gene. Galactosyltransferase I catalyzes the synthesis of the glycosaminoglycan-protein linkage in proteoglycans. Proteoglycans in turn are structural components of the extracellular matrix that is found between cells in connective tissues.

Function

Galactosyltransferase I is one of seven β-1,4-galactosyltransferase (β4GalT) enyzmes. These enzymes are type II membrane-bound glycoproteins that appear to have exclusive specificity for the donor substrate UDP-galactose; all transfer galactose in a β-1,4 linkage to similar acceptor sugars: GlcNAc, Glc, and Xyl. Each beta4GalT has a distinct function in the biosynthesis of different glycoconjugates and saccharide structures. As type II membrane proteins, they have an N-terminal hydrophobic signal sequence that directs the protein to the Golgi apparatus and which then remains uncleaved to function as a transmembrane anchor. By sequence similarity, the beta4GalTs form four groups: β4GalT1 and β4GalT2, β4GalT3 and β4GalT4, β4GalT5 and β4GalT6, and β4GalT7. The enzyme encoded by this gene attaches the first galactose in the common carbohydrate-protein (GlcA-β-1,3-Gal-β-1,3-Gal-β-1,4-Xyl-beta1-O-Ser) linkage found in proteoglycans. Manganese is required as a cofactor. This enzyme differs from the other six beta4GalTs because it lacks the conserved β4GalT1-β4GalT6 Cys residues and it is located in cis-Golgi instead of trans-Golgi.

Clinical significance

Mutations in the B4GALT7 gene that result in a defective galactosyltransferase I enzyme with reduced or absent activity are associated with progeroid type Ehlers-Danlos syndrome.

Further reading

• Amado M, Almeida R, Schwientek T, Clausen H (2000). "Identification and characterization of large galactosyltransferase gene families: galactosyltransferases for all functions". Biochim. Biophys. Acta 1473 (1): 35–53. doi:10.1016/S0304-4165(99)00168-3. PMID 10580128. 
• Seidler DG, Faiyaz-Ul-Haque M, Hansen U, et al. (2007). "Defective glycosylation of decorin and biglycan, altered collagen structure, and abnormal phenotype of the skin fibroblasts of an Ehlers-Danlos syndrome patient carrying the novel Arg270Cys substitution in galactosyltransferase I (beta4GalT-7)". J. Mol. Med. 84 (7): 583–94. doi:10.1007/s00109-006-0046-4. PMID 16583246. 
• Gulberti S, Lattard V, Fondeur M, et al. (2005). "Phosphorylation and sulfation of oligosaccharide substrates critically influence the activity of human beta1,4-galactosyltransferase 7 (GalT-I) and beta1,3-glucuronosyltransferase I (GlcAT-I) involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans". J. Biol. Chem. 280 (2): 1417–25. doi:10.1074/jbc.M411552200. PMID 15522873. 
• Gerhard DS, Wagner L, Feingold EA, et al. (2004). "The Status, Quality, and Expansion of the NIH Full-Length cDNA Project: The Mammalian Gene Collection (MGC)". Genome Res. 14 (10B): 2121–7. doi:10.1101/gr.2596504. PMC 528928. PMID 15489334. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=528928. 
• Ota T, Suzuki Y, Nishikawa T, et al. (2004). "Complete sequencing and characterization of 21,243 full-length human cDNAs". Nat. Genet. 36 (1): 40–5. doi:10.1038/ng1285. PMID 14702039. 
• Clark HF, Gurney AL, Abaya E, et al. (2003). "The Secreted Protein Discovery Initiative (SPDI), a Large-Scale Effort to Identify Novel Human Secreted and Transmembrane Proteins: A Bioinformatics Assessment". Genome Res. 13 (10): 2265–70. doi:10.1101/gr.1293003. PMC 403697. PMID 12975309. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=403697. 
• Strausberg RL, Feingold EA, Grouse LH, et al. (2003). "Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences". Proc. Natl. Acad. Sci. U.S.A. 99 (26): 16899–903. doi:10.1073/pnas.242603899. PMC 139241. PMID 12477932. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=139241. 
• Kuroiwa A, Matsuda Y, Okajima T, Furukawa K (2000). "Assignment of human xylosylprotein beta-1,4-galactosyltransferase gene (B4GALT7) to human chromosome 5q35.2→q35.3 by in situ hybridization". Cytogenet. Cell Genet. 89 (1–2): 8–9. doi:10.1159/000015578. PMID 10894925. 
• Kresse H, Rosthøj S, Quentin E, et al. (1987). "Glycosaminoglycan-free small proteoglycan core protein is secreted by fibroblasts from a patient with a syndrome resembling progeroid". Am. J. Hum. Genet. 41 (3): 436–53. PMC 1684193. PMID 3631078. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1684193.