B4GALT7

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.

B4GALT7
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 4IRP, 4IRQ
Identifiers
Aliases	B4GALT7, EDSP1, XGALT1, XGPT1, EDSSLA, beta-1,4-galactosyltransferase 7, EDSSPD1, XGPT
External IDs	OMIM: 604327; MGI: 2384987; HomoloGene: 5248; GeneCards: B4GALT7; OMA:B4GALT7 - orthologs
Gene location (Human) Chr. Chromosome 5 (human) Band 5q35.3 Start 177,600,132 bp End 177,610,330 bp
Gene location (Mouse) Chr. Chromosome 13 (mouse) Band 13|13 B1 Start 55,747,709 bp End 55,758,256 bp
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in tendon of biceps brachii right adrenal gland left adrenal gland left adrenal cortex right adrenal cortex anterior pituitary apex of heart body of pancreas stromal cell of endometrium body of stomach Top expressed in saccule otic vesicle otic placode cumulus cell renal corpuscle medullary collecting duct decidua granulocyte blood internal carotid artery More reference expression data BioGPS More reference expression data
Gene ontology Molecular function transferase activity manganese ion binding glycosyltransferase activity metal ion binding galactosyltransferase activity protein binding beta-N-acetylglucosaminylglycopeptide beta-1,4-galactosyltransferase activity xylosylprotein 4-beta-galactosyltransferase activity Cellular component integral component of membrane Golgi apparatus membrane Golgi membrane Golgi cisterna membrane Biological process glycosaminoglycan metabolic process protein glycosylation proteoglycan metabolic process glycosaminoglycan biosynthetic process protein N-linked glycosylation negative regulation of fibroblast proliferation supramolecular fiber organization carbohydrate metabolic process Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 11285 218271 Ensembl ENSG00000027847 ENSMUSG00000021504 UniProt Q9UBV7 Q8R087 RefSeq (mRNA) NM_007255 NM_146045 NM_001311137 RefSeq (protein) NP_009186 NP_001298066 NP_666157 Location (UCSC) Chr 5: 177.6 – 177.61 Mb Chr 13: 55.75 – 55.76 Mb PubMed search
Wikidata
View/Edit Human View/Edit Mouse

Function

Galactosyltransferase I is one of seven β-1,4-galactosyltransferase (β4GalT) enzymes. 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 Spondylodysplastic, formerly progeroid type Ehlers-Danlos syndrome. The reduced activity of B4GALT7 is associated with a reduced substitution of the proteoglycans decorin and biglycan with glycosaminoglycan carbohydrate chains, and with alterations in heparan sulfate biosynthesis, resulting in delayed wound repair, altered migration, adhesion and contractility of patient fibroblasts. 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.

External links

• Human B4GALT7 genome location and B4GALT7 gene details page in the UCSC Genome Browser.
• PDBe-KB provides an overview of all the structure information available in the PDB for Human Beta-1,4-galactosyltransferase 7

Further reading

• Amado M, Almeida R, Schwientek T, Clausen H (December 1999). "Identification and characterization of large galactosyltransferase gene families: galactosyltransferases for all functions". Biochimica et Biophysica Acta (BBA) - General Subjects. 1473 (1): 35–53. doi:10.1016/S0304-4165(99)00168-3. PMID 10580128.
• Seidler DG, Faiyaz-Ul-Haque M, Hansen U, Yip GW, Zaidi SH, Teebi AS, et al. (July 2006). "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)". Journal of Molecular Medicine. 84 (7): 583–94. doi:10.1007/s00109-006-0046-4. PMID 16583246. S2CID 10165577.
• Gulberti S, Lattard V, Fondeur M, Jacquinet JC, Mulliert G, Netter P, et al. (January 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". The Journal of Biological Chemistry. 280 (2): 1417–25. doi:10.1074/jbc.M411552200. PMID 15522873.
• 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". Cytogenetics and Cell Genetics. 89 (1–2): 8–9. doi:10.1159/000015578. PMID 10894925. S2CID 33696165.
• Kresse H, Rosthøj S, Quentin E, Hollmann J, Glössl J, Okada S, Tønnesen T (September 1987). "Glycosaminoglycan-free small proteoglycan core protein is secreted by fibroblasts from a patient with a syndrome resembling progeroid". American Journal of Human Genetics. 41 (3): 436–53. PMC 1684193. PMID 3631078.