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Xylosylprotein beta 1,4-galactosyltransferase, polypeptide 7
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols B4GALT7 ; EDSP1; XGALT1; XGPT1
External IDs OMIM604327 MGI2384987 HomoloGene5248 GeneCards: B4GALT7 Gene
EC number
RNA expression pattern
PBB GE B4GALT7 53076 at tn.png
PBB GE B4GALT7 222191 s at tn.png
More reference expression data
Species Human Mouse
Entrez 11285 218271
Ensembl ENSG00000027847 ENSMUSG00000021504
UniProt Q9UBV7 Q8R087
RefSeq (mRNA) NM_007255 NM_146045
RefSeq (protein) NP_009186 NP_666157
Location (UCSC) Chr 5:
177.03 – 177.04 Mb
Chr 13:
55.6 – 55.61 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.[1][1][2][2][3] Galactosyltransferase I catalyzes the synthesis of the glycosaminoglycan-protein linkage in proteoglycans.[4] Proteoglycans in turn are structural components of the extracellular matrix that is found between cells in connective tissues.


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.[3]

Clinical significance[edit]

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.[2][4][5][6] Since mutations in B4GALT7 impair a glycosylation pathway, the resulting subtype of Ehlers-Danlos syndrome may be considered a congenital disorder of glycosylation (CDG), according to the new CDG nomenclature.

Mutations in B4GALT7 cause Larsen syndrome .Cartault, F; Munier, P; Jacquemont, M. L.; Vellayoudom, J; Doray, B; Payet, C; Randrianaivo, H; Laville, J. M.; Munnich, A; Cormier-Daire, V (2014). "Expanding the clinical spectrum of B4GALT7 deficiency: Homozygous p.R270C mutation with founder effect causes Larsen of Reunion Island syndrome". European Journal of Human Genetics 23: 49–53. doi:10.1038/ejhg.2014.60. PMID 24755949.  edit


  1. ^ a b Okajima T, Yoshida K, Kondo T, Furukawa K (Sep 1999). "Human homolog of Caenorhabditis elegans sqv-3 gene is galactosyltransferase I involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans". J Biol Chem 274 (33): 22915–8. doi:10.1074/jbc.274.33.22915. PMID 10438455. 
  2. ^ a b c Almeida R, Levery SB, Mandel U, Kresse H, Schwientek T, Bennett EP, Clausen H (Oct 1999). "Cloning and expression of a proteoglycan UDP-galactose:beta-xylose beta1,4-galactosyltransferase I. A seventh member of the human beta4-galactosyltransferase gene family". J Biol Chem 274 (37): 26165–71. doi:10.1074/jbc.274.37.26165. PMID 10473568. 
  3. ^ a b "Entrez Gene: B4GALT7 xylosylprotein beta 1,4-galactosyltransferase, polypeptide 7 (galactosyltransferase I)". 
  4. ^ a b Okajima T, Fukumoto S, Furukawa K, Urano T (October 1999). "Molecular basis for the progeroid variant of Ehlers-Danlos syndrome. Identification and characterization of two mutations in galactosyltransferase I gene". J. Biol. Chem. 274 (41): 28841–4. doi:10.1074/jbc.274.41.28841. PMID 10506123. 
  5. ^ Quentin E, Gladen A, Rodén L, Kresse H. (Aug 1990). "A genetic defect in the biosynthesis of dermatan sulfate proteoglycan: galactosyltransferase I deficiency in fibroblasts from a patient with a progeroid syndrome.". Proceedings of the National Academy of Sciences of the United States of America 87 (4): 1342–6. doi:10.1073/pnas.87.4.1342. PMC 53471. PMID 2106134. 
  6. ^ Furukawa K, Okajima T (December 2002). "Galactosyltransferase I is a gene responsible for progeroid variant of Ehlers-Danlos syndrome: molecular cloning and identification of mutations". Biochim. Biophys. Acta 1573 (3): 377–81. doi:10.1016/S0304-4165(02)00406-3. PMID 12417421. 

Further reading[edit]