There are five identified human EXT family proteins (EXT1, EXT2, EXTL1, EXTL2 and EXTL3), which are members of the hereditary multiple exostoses family of tumour suppressors []. Exostosin-2 (EXT2) is a glycosyltransferase required for the biosynthesis of heparan-sulfate []. Hereditary multiple exostoses, a genetic disorder characterised by multiple cartilaginous tumours, is caused by mutations in members of the EXT gene family, EXT1 or EXT2. EXT1 and EXT2 form a hetero-oligomeric complex that leads to the accumulation of both proteins in the Golgi apparatus []. The Golgi-localised EXT1/EXT2 complex possesses substantially higher glycosyltransferase activity than EXT1 or EXT2 alone [].
There are five identified human EXT family proteins (EXT1, EXT2, EXTL1, EXTL2 and EXTL3), which are members of the hereditary multiple exostoses family of tumor suppressors []. Exostosin-1 (EXT1) is a glycosyltransferase required for the biosynthesis of heparan-sulfate []. Hereditary multiple exostoses, a genetic disorder characterised by multiple cartilaginous tumors, is caused by mutations in members of the EXT gene family, EXT1 or EXT2. EXT1 and EXT2 form a hetero-oligomeric complex that leads to the accumulation of both proteins in the Golgi apparatus [].
There are five identified human EXT family proteins (EXT1, EXT2, EXTL1, EXTL2 and EXTL3), which are members of the hereditary multiple exostoses family of tumor suppressors []. They are glycosyltransferases required for the biosynthesis of heparan sulfate. Hereditary multiple exostoses (EXT) is an autosomal dominant disorder that is characterised by the appearance of multiple outgrowths of the long bones (exostoses) at their epiphyses []. Mutations in two homologous genes, EXT1 and EXT2, are responsible for the EXT syndrome. The human and mouse EXT genes have at least two homologues in the invertebrate Caenorhabditis elegans, indicating that they do not function exclusively as regulators of bone growth. EXT1 and EXT2 have both been shown to encode glycosyltransferases involved in the chain elongation step of heparan sulphate biosynthesis [].This entry also includes Arabidopsis Xyloglucan galactosyltransferase KATAMARI1 []and Drosophila melanogaster EXT homologues [].
There are five identified human EXT family proteins (EXT1, EXT2, EXTL1, EXTL2 and EXTL3), which are members of the hereditary multiple exostoses family of tumor suppressors []. They are glycosyltransferases required for the biosynthesis of heparan sulfate. Hereditary multiple exostoses (EXT) is an autosomal dominant disorder that is characterised by the appearance of multiple outgrowths of the long bones (exostoses) at their epiphyses []. Mutations in two homologous genes, EXT1 and EXT2, are responsible for the EXT syndrome. The human and mouse EXT genes have at least two homologues in the invertebrate Caenorhabditis elegans, indicating that they do not function exclusively as regulators of bone growth. EXT1 and EXT2 have both been shown to encode glycosyltransferases involved in the chain elongation step of heparan sulphate biosynthesis [].In addition to a b-glucuronyltransferase domain, exostosins contain anadditional alpha 1,4-N-acetylglucosaminyltransferase domain that belongs to family GT64 [, ]. Activities of both exostosin GT domains are required for synthesizing the backbone of glycosaminoglycan, heparan sulfate. In plants, many genes have been shown to encode proteins with significant sequence similarity to the exostosinb-glucuronyltransferase domain and therefore are grouped into family GT47 []. This entry represents the GT47 domain of exostosins.
