Galactosylation of collagen propeptide hydroxylysines by procollagen galactosyltransferases 1, 2.

Stable Identifier
R-HSA-1981120
Type
Reaction [transition]
Species
Homo sapiens
Compartment
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Hydroxylysine glycosides are specific to collagen. Collagen glycosylation takes place in the endoplasmic reticulum before triple-helix formation. Either galactose or glucose-galactose are attached to approximately one third of hydroxylysine residues by specific transferases, beta(1-O)galactosyl- and alpha(1-2)glucosyltransferase, forming galactosyl hydroxylysine (Gal-Hyl) and glucosyl-galactosyl hydroxylysine (Glu-Gal-Hyl) respectively. The genes GLT25D1 and GLT25D2 encode galactosyltransferases that are active with various types of collagen and the serum mannose-binding lectin MBL, which also contains a collagen domain. GLT25D1 gene is constitutively expressed in human tissues, whereas the GLT25D2 gene was found to be expressed only at low levels in the nervous system. These galactosyltransferases convert 5-hydroxylysine to 5-galactosyl hydroxylysine (Gal-Hyl). The extent of hydroxylysine galactosylation is variable between collagen types and locations; it is particularly common in bone type I collagen (Al-Dehaimi et al. 1999). Although the fraction of hydroxylysine residues that are glycosylated does not differ between skin and bone (the major sources of type I collagen) the pattern of hydroxylysine glycosylation is different. Glu-Gal-Hyl predominates in skin, where the Glu-Gal-Hyl/Gal-Hyl ratio is approximately 2 (Pinnell et al. 1971), whereas Gal-Hyl predominates in bone, where the Glu-Gal-Hyl/Gal-Hyl ratio is 0.47 (Krane et al. 1977).

Literature References
PubMed ID Title Journal Year
19075007 Core glycosylation of collagen is initiated by two beta(1-O)galactosyltransferases

Schegg, B, Hülsmeier, AJ, Rutschmann, C, Maag, C, Hennet, T

Mol Cell Biol 2009
20470363 The human collagen beta(1-O)galactosyltransferase, GLT25D1, is a soluble endoplasmic reticulum localized protein

Liefhebber, JM, Punt, S, Spaan, WJ, van Leeuwen, HC

BMC Cell Biol 2010
Participants
Participant Of
Catalyst Activity
Catalyst Activity
Title
procollagen galactosyltransferase activity of COLGALT1,COLGALT2:Lysyl hydroxylated collagen propeptides [endoplasmic reticulum lumen]
Physical Entity
Activity
Orthologous Events
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Created