Table 2.
Biosynthetic enzymes of the GAG-linkage region tetrasaccharide.
| Enzymes (activity) |
Coding genes (synonym) |
Chromosomal location | mRNA accession number | MIM number | Human genetic disorders | Clinical features | References for the human diseases | References for the knockout mice |
|---|---|---|---|---|---|---|---|---|
| Xylosyltransferase (XylT) |
XYLT1 | 16p12.3 | NM_022166 | 608124 | Desbuquois dysplasia type 2, Short stature syndrome | Short stature, joint laxity, advanced carpal ossification, and hand anomalies. | [56–58] | [59] |
| XYLT2 | 17q21.33 | NM_022167 | 608125 | — | — | — | [60] | |
|
| ||||||||
|
β4-Galactosyltransferase-I (GalT-I) |
B4GALT7 | 5q35.2-q35.3 | NM_007255 | 130070 604327 |
Ehlers-Danlos syndrome progeroid type 1 Larsen of Reunion Island syndrome |
Developmental delay, aged appearance, short stature, craniofacial dysmorphism, and generalized osteopenia. Multiple dislocations, hyperlaxity, dwarfism, and distinctive facial features. |
[61–69] | — |
|
| ||||||||
|
β3-Galactosyltransferase-II (GalT-II) |
B3GALT6 | 1p36.33 | NM_080605 | 271640 615349 615291 |
Ehlers-Danlos syndrome progeroid type 2 Spondyloepimetaphyseal dysplasia with joint laxity type 1 |
Sparse hair, wrinkled skin, defective wound healing with atrophic scars, osteopenia, and radial head dislocation. Spatulate finger with short nail, hip dislocation, elbow contracture, clubfeet, and mild craniofacial dysmorphism including prominent eye, blue sclera, long upper lip, and small mandible with cleft palate. |
[70–72] | — |
|
| ||||||||
|
β3-Glucuronyltransferase-I (GlcAT-I) |
B3GAT3 | 11q12.3 | NM_012200 | 245600 606374 |
Larsen-like syndrome B3GAT3 type Multiple joint dislocations, short stature, craniofacial dysmorphism, and congenital heart defects |
Joint dislocations mainly affecting the elbow, congenital heart defects such as bicuspid aortic valve, aortic root dilatation. | [73, 74] | [75, 76] |
|
| ||||||||
| Xylose 2-O-kinase |
FAM20B
(GXK1) |
1q25 | NM_014864 | 611063 | — | — | — | — |
|
| ||||||||
| Xylose 2-O-phosphatase |
ACPL2
(XYLP) |
3q23 | NM_152282 | — | — | — | — | — |
—, not reported.
B4GALT7: xylosylprotein beta 1,4-galactosyltransferase 7; B3GALT6, beta 1,3-galactosyltransferase 6; B3GAT3, beta 1,3-glucuronyltransferase 3; FAM20B, Family with sequence similarity 20 member B; ACPL2, acid phosphatase-like 2.