Figure 7
From: Sulfation of sialic acid is ubiquitous and essential for vertebrate development
O-Sulfation and O-acetylation of Sia occur at different metabolite levels in the Golgi. For sialoglycans (Sia-glycans) biosynthesis, sialic acid (Sia) is first activated to CMP-sialic acid (CMP-Sia) by CMP-Sia synthetase (CMAS) in the cytosol and/or nucleus. CMP-Sia is then transported into the Golgi lumen by CMP-Sia transporter (CST), and used as a donor substrate of sialyltransferases (SialylT) to synthesize Sia-glycans on proteins and lipids. 9-O-Acetylation of Sia occurs at the CMP-Sia level using acetyl-coenzyme A (AcCoA) as a donor and 9-O-acetylated Sia (Sia9Ac) residue is synthesized by SialylT using CMP-Sia9Ac as a substrate. In contrast, 8-O-sulfation occurs at the Sia-glycan level using 3′-phosphoadenosine 5′-phosphosulfate (PAPS) as a donor, forming 8-O-sulfated Sia (Sia8S)-glycans. CASD1 Cas domain containing 1, Wscd1 Wsc domain containing 1, Wscd2 Wsc domain containing 2.
