PAPS (3'-phosphoadenosine-5'-phosphosulfate), which functions as a sulfate donor in the cell, is synthesized from sulfate and two molecules of ATP in a two-step process (Robbins & Lipmann 1958) catalyzed in vertebrates by a bifunctional enzyme (Venkatachalam et al. 1998). PAPS synthesis takes place in the cytosol, and it is either consumed there in the sulfonation of a variety of hormones and xenobiotics, or it is transported to the Golgi apparatus and consumed in the synthesis of proteoglycans like chondroitin sulfate. Two isoforms of the human bifunctional enzyme are known, mutations in one of which are associated with defects in proteoglycan biosynthesis (Girard et al. 1998, ul Haque et al. 1998).
Superti-Furga, A, Krakow, D, Ahmad, W, Cohn, DH, Rusiniak, ME, Haque, S, Abbas, H, King, LM, Ahmad, M, Swank, RT, ul Haque, MF, Cantor, RM
Girard, JP, Baekkevold, ES, Amalric, F
Venkatachalam, KV, Akita, H, Strott, CA
Lipmann, F, Robbins, PW
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