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.
Uyama, T, Kitagawa, H, Sugahara, K
Yada, T, Kwon, YD, Kudo, T, Iwasaki, H, Gotoh, M, Watanabe, H, Go, M, Togayachi, A, Kimata, K, Sato, T, Kaseyama, H, Shionyu, M, Narimatsu, H, Kikuchi, N
Yada, T, Kwon, YD, Sato, T, Kudo, T, Iwasaki, H, Gotoh, M, Watanabe, H, Kaseyama, H, Narimatsu, H, Togayachi, A, Kikuchi, N, Kimata, K
glucuronosyl-N-acetylgalactosaminyl-proteoglycan 4-beta-N-acetylgalactosaminyltransferase activity of CHPF,CHSY3 [Golgi membrane]
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