Information on EC 2.4.1.134 - galactosylxylosylprotein 3-beta-galactosyltransferase

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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria

EC NUMBER
COMMENTARY hide
2.4.1.134
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RECOMMENDED NAME
GeneOntology No.
galactosylxylosylprotein 3-beta-galactosyltransferase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
UDP-alpha-D-galactose + 4-beta-D-galactosyl-O-beta-D-xylosyl-[protein] = UDP + 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylosyl-[protein]
show the reaction diagram
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
hexosyl group transfer
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
Glycosaminoglycan biosynthesis - chondroitin sulfate / dermatan sulfate
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Glycosaminoglycan biosynthesis - heparan sulfate / heparin
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glycosaminoglycan-protein linkage region biosynthesis
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Metabolic pathways
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SYSTEMATIC NAME
IUBMB Comments
UDP-galactose:4-beta-D-galactosyl-O-beta-D-xylosylprotein 3-beta-D-galactosyltransferase
Involved in the biosynthesis of the linkage region of glycosaminoglycan chains as part of proteoglycan biosynthesis (chondroitin, dermatan and heparan sulfates). Requires Mn2+.
CAS REGISTRY NUMBER
COMMENTARY hide
56626-19-8
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56626-21-2
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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Manually annotated by BRENDA team
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
malfunction
enzyme deficiency alters synthesis of both main types of glycosaminoglycans and results in impaired wound repair in vivo with abnormal dermal collagen fibril architecture characterized by loosely packed collagen fibrils of variable size and shape; loss of function of gene b3GalT6 causes a severe deficiency in glycosaminoglycan synthesis and results in the production of immature decorin, lacking its chondroitin sulfate/dermatan sulfate side chain, as well as reduced-to-absent heparan sulfate chains in dermal fibroblasts of affected individuals. Homozygosity mapping and candidate gene sequence analysis in three independent families identified biallelic gene B3GALT6 mutations, including homozygous missense, the families present a severe autosomal-recessive connective tissue disorder characterized by skin fragility, delayed wound healing, joint hyperlaxity and contractures, muscle hypotonia, intellectual disability, and a spondyloepimetaphyseal dysplasia with bone fragility and severe kyphoscoliosis. The phenotype overlaps with several recessive Ehlers-Danlos variants and spondyloepimetaphyseal dysplasia with joint hyperlaxity. Affected individuals' fibroblasts exhibit a large decrease in ability to prime glycosaminoglycan synthesis together with impaired glycanation of the small chondroitin/dermatan sulfate proteoglycan decorin, confirming b3GalT6 loss of function. Dermal electron microcopy discloses abnormalities in collagen fibril organization, in line with the important regulatory role of decorin in this process. A strong reduction in heparan sulfate level is also observed, indicating that enzyme b3GalT6 deficiency alters synthesis of both main types of glycosaminoglycans. In vitro wound healing assay reveals a significant delay in fibroblasts from two index individuals, pointing to a role for glycosaminoglycan defect in impaired wound repair in vivo. Genotype-Phenotype-analysis, overview
metabolism
the enzyme catalyzes a step in glycosaminoglycan synthesis, pathway overview
physiological function
proteoglycans are important components of cell plasma membranes and extracellular matrices of connective tissues. They consist of glycosaminoglycan chains attached to a core protein via a tetrasaccharide linkage, whereby addition of the third residue is catalyzed by galactosyltransferase II, encoded by gene B3GALT6. A crucial role for b3GalT6 in multiple major developmental and pathophysiological processes
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
UDP-alpha-D-galactose + 4-beta-D-galactosyl-O-beta-D-xylosyl-[protein]
UDP + 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylosyl-[protein]
show the reaction diagram
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-
?
UDP-alpha-D-galactose + 4-methylumbelliferyl-beta-D-xylopyranoside
UDP + ?
show the reaction diagram
-
-
-
?
UDP-galactose + 4-beta-D-galactosyl-O-beta-D-xylose
UDP + 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylose
show the reaction diagram
UDP-galactose + 4-beta-D-galactosyl-O-beta-D-xylosylprotein
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-1,4-beta-D-xylosylprotein
show the reaction diagram
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involved in biosynthesis of chondroitin sulfate
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UDP-galactose + beta-D-galactosyl-1,3-beta-galactosyl-O-naphthalenemethanol
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-1,3-beta-galactosyl-O-naphthalenemethanol
show the reaction diagram
UDP-galactose + beta-D-galactosyl-1,3-N-acetyl-alpha-D-glucosaminyl-O-naphthalenemethanol
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-1,3-N-acetyl-alpha-D-glucosaminyl-O-naphthalenemethanol
show the reaction diagram
UDP-galactose + beta-D-galactosyl-1,3-N-acetyl-beta-D-glucosaminyl-O-naphthalenemethanol
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-1,3-N-acetyl-beta-D-glucosaminyl-O-naphthalenemethanol
show the reaction diagram
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?
UDP-galactose + beta-D-galactosyl-1,4-beta-D-xylosyl-O-benzyl
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-1,4-beta-D-xylosyl-O-benzyl
show the reaction diagram
UDP-galactose + beta-D-galactosyl-1,4-N-acetyl-beta-D-glucosaminyl-O-naphthalenemethanol
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-1,4-N-acetyl-beta-D-glucosaminyl-O-naphthalenemethanol
show the reaction diagram
UDP-galactose + beta-D-galactosyl-O-naphthalenemethanol
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-O-naphthalenemethanol
show the reaction diagram
UDP-galactose + beta-galactosides
?
show the reaction diagram
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e.g. phenyl or pyridine 3-O-beta-galactosides, poor substrate: pyridine 2-S-beta-thiogalactoside, no substrate: D-galactose
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UDP-galactose + galactosyl-xylosylserine
UDP + 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylosylserine
show the reaction diagram
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?
UDP-galactose + Galalpha-p-nitrophenol
?
show the reaction diagram
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?
UDP-galactose + Galbeta-p-nitrophenol
?
show the reaction diagram
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?
UDP-galactose + Galbeta1,4Xyl-p-methoxyphenol
?
show the reaction diagram
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?
UDP-galactose + N-acetyl-beta-D-glucosaminyl-1,3-beta-D-galactosyl-O-naphthalenemethanol
UDP + beta-D-galactosyl-1,3-N-acetyl-beta-D-glucosaminyl-1,3-beta-D-galactosyl-O-naphthalenemethanol
show the reaction diagram
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?
UDP-galactose + pyridine 3-O-beta-D-galactoside
UDP + ?
show the reaction diagram
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?
additional information
?
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
UDP-alpha-D-galactose + 4-beta-D-galactosyl-O-beta-D-xylosyl-[protein]
UDP + 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylosyl-[protein]
show the reaction diagram
Q96L58
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?
UDP-galactose + 4-beta-D-galactosyl-O-beta-D-xylosylprotein
UDP + beta-D-galactosyl-1,3-beta-D-galactosyl-1,4-beta-D-xylosylprotein
show the reaction diagram
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involved in biosynthesis of chondroitin sulfate
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additional information
?
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dbeta3GalTII is involved in heparan sulfate synthesis for wing and eye development. dbeta3GalTII contributes to heparan sulfate proteoglycan synthesis in vitro and in vivo and also modulates Wingless distribution
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Mn2+
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requirement
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
100
pyridine 3-O-beta-galactoside
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pH 6, 37°C, value above
1.05
UDPgalactose
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pH 6, 37°C, + pyridine 3-O-beta-galactoside
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
3
pmol/h/ml medium, beta-D-galactosyl-1,3-beta-D-galactosyl-O-naphthalenemethanol as substrate
2660
pmol/h/ml medium, beta-D-galactosyl-1,4-beta-xylosyl-O-benzyl as substrate
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
6
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broad, beta-galactosides
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
37
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assay at
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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m-RNA expression
Manually annotated by BRENDA team
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epiphyses from embryonic femurs and tibiae
Manually annotated by BRENDA team
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central nervous system, eye disc, leg disc, wing disc. Low activity in salivary gland
Manually annotated by BRENDA team
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
33400
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calculated from nucleotide sequence
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
50
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60 min, about 40% loss of activity, beta-galactosides
60
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t1/2: 7 min, beta-galactosides
STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
-20°C, microsomal enzyme preparation, at least 12 months
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
partial
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expression in Caenorhabditis elegans; transient expression as a fusion protein with protein A in chinese hamster ovary cells COS-1
expression in Haemophilus ducreyi strain A77
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expression in Spodoptera frugiperda Sf9 cells
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gene B3GALT6, homozygosity mapping and candidate gene sequence analysis in three independent families, genotyping
transient expression as a fusion protein with protein A in chinese hamster ovary cells COS-1
EXPRESSION
ORGANISM
UNIPROT
LITERATURE
there is no significant effect of Sry-type high-mobility-group box 9 transduction on the gene expression of galactosyltransferase-2
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
A108G
naturally occuring enzyme mutation
D207H
naturally occuring enzyme mutation
G217S
naturally occuring enzyme mutation
additional information
homozygosity mapping and candidate gene sequence analysis in three independent families identified biallelic gene B3GALT6 mutations, including homozygous missense mutations in family 1 (c.619G>C [p.Asp207His]) and family 3 (c.649G>A [p.Gly217Ser]) and compound heterozygous mutations in family 2 (c.323_344del [p.Ala108Glyfs*163], c.619G>C [p.Asp207His]), phenotypes overview