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

Stable Identifier
Reaction [transition]
Homo sapiens
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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
Participant Of
Catalyst Activity
Catalyst Activity
procollagen galactosyltransferase activity of COLGALT1,COLGALT2:Lysyl hydroxylated collagen propeptides [endoplasmic reticulum lumen]
Physical Entity
Orthologous Events