Chondroitin sulfate synthases (CHSY) are involved in the synthesis of chondroitin sulfate, adding alternatingly glucuronate (GlcA) and N-acetylgalactosamine (GalNAc) to the growing chondroitin polymer (Mizumoto et al. 2013). Defects in CHSY1 cause temtamy preaxial brachydactyly syndrome (TPBS; MIM:605282), a syndrome characterized by multiple congenital anomalies, mental retardation, sensorineural deafness, growth retardation and bilateral symmetric digital anomalies mainly in the form of preaxial brachydactyly (literally, shortness of fingers and toes) and hyperphalangism (Temtamy et al. 1998, Race et al. 2010, Tian et al. 2010).
A glucuronate (GlcA) moiety is added to the chondroitin chain by dual-activity enzymes, the chondroitin sulfate synthases 1-3 (CHSY1, CHPF and CHSY3) (Kitagawa et al. 2001, Yada et al. 2003, Yada et al. 2003b). They possess both beta-1,3-glucuronic acid and beta-1,4-N-acetylgalactosamine transferase activity. These three enzymes require divalent metals as cofactors, manganese producing the highest activities. Another candidate enzyme, chondroitin sulfate glucuronyltransferase (CHPF2) possess only beta-1,3-glucuronic acid transferase activity (Izumikawa et al. 2008, Gotoh et al. 2002). Defects in CHSY1 cause Temtamy preaxial brachydactyly syndrome (TPBS) (MIM:605282) (Tian et al. 2010, Li et al. 2010).
An N-acetylgalactosamine (GalNAc) moiety is added to the chondroitin chain by dual-activity enzymes, the chondroitin sulfate synthases 1-3 (CHSY1, CHPF and CHSY3 respectively) (Kitagawa et al. 2001, Yada et al. 2003, Yada et al. 2003b). They possess both beta-1,3-glucuronic acid and beta-1,4-N-acetylgalactosamine transferase activity, the latter activity used in this reaction. These three enzymes require divalent metals as cofactors, manganese producing the highest activities. The repeated disaccharide units of GlcA-GalNAc identify this glycosaminoglycan as chondroitin.
Chondroitin sulfate synthase 1 (CHSY1) (Kitagawa et al. 2001) possesses both beta-1,3-glucuronic acid and beta-1,4-N-acetylgalactosamine transferase activity, adding alternatingly the two building blocks GlcA and GalNAc to the growing chondroitin chain. Complete or almost complete loss of CHSY1 results in temtamy preaxial brachydactyly syndrome (TPBS; MIM:605282), an autosomal recessive characterized by limb malformations, short stature, and hearing loss. Mutations in CHSY1 leading to loss of function include E33Sfs*34, G19_L28del, P539R and Q69* (Temtamy et al. 1998, Li et al. 2010).
Chondroitin sulfate synthase 1 (CHSY1) (Kitagawa et al. 2001) possesses both beta-1,3-glucuronate (GlcA) and beta-1,4-N-acetylgalactosamine (GalNAc) transferase activity, added alternatingly the two building blocks GlcA and GalNAc to the growing chondroitin chain. Complete or almost complete loss of CHSY1 results in temtamy preaxial brachydactyly syndrome (TPBS; MIM:605282), an autosomal recessive characterized by limb malformations, short stature, and hearing loss. Mutations in CHSY1 leading to loss of function include E33Sfs*34, G19_L28del, P539R and Q69* (Temtamy et al. 1998, Li et al. 2010).
A glucuronate (GlcA) moiety is added to the chondroitin chain by dual-activity enzymes, the chondroitin sulfate synthases 1-3 (CHSY1, CHPF and CHSY3) (Kitagawa et al. 2001, Yada et al. 2003, Yada et al. 2003b). They possess both beta-1,3-glucuronic acid and beta-1,4-N-acetylgalactosamine transferase activity. These three enzymes require divalent metals as cofactors, manganese producing the highest activities. Another candidate enzyme, chondroitin sulfate glucuronyltransferase (CHPF2) possess only beta-1,3-glucuronic acid transferase activity (Izumikawa et al. 2008, Gotoh et al. 2002). Defects in CHSY1 cause Temtamy preaxial brachydactyly syndrome (TPBS) (MIM:605282) (Tian et al. 2010, Li et al. 2010).
An N-acetylgalactosamine (GalNAc) moiety is added to the chondroitin chain by dual-activity enzymes, the chondroitin sulfate synthases 1-3 (CHSY1, CHPF and CHSY3 respectively) (Kitagawa et al. 2001, Yada et al. 2003, Yada et al. 2003b). They possess both beta-1,3-glucuronic acid and beta-1,4-N-acetylgalactosamine transferase activity, the latter activity used in this reaction. These three enzymes require divalent metals as cofactors, manganese producing the highest activities. The repeated disaccharide units of GlcA-GalNAc identify this glycosaminoglycan as chondroitin.