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hs6st3b is one of the zebrafish HS 6-O-sulfotransferase paralogs (hs6st1a, hs6st1b, hs6st2,
hs6st3a, hs6st3b), confirming target identity as a Danio rerio HS6ST3 family member.
"explicitly lists **hs6st3b** among zebrafish 6-O-sulfotransferases (hs6st1a, hs6st1b, hs6st2, hs6st3a, **hs6st3b**)"
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HS6ST enzymes transfer a sulfo group to the 6-hydroxyl of glucosamine residues within HS
chains, generating 6-O-sulfated HS motifs.
"transfer of a sulfo group to the **6-hydroxyl of glucosamine residues** within HS chains"
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HS6STs use PAPS (3'-phosphoadenosine 5'-phosphosulfate) as the universal sulfate donor,
producing PAP as a product.
"HS6STs use **PAPS (3′-phosphoadenosine-5′-phosphosulfate)** as the universal sulfate donor (producing PAP as a product)"
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Sequence analysis of zebrafish Hs6st enzymes identifies an N-terminal hydrophobic segment
consistent with a type II transmembrane protein and infers Golgi apparatus localization, the
expected site of HS chain modification during proteoglycan biosynthesis.
"consistent with a **type II transmembrane protein** and the authors infer **Golgi apparatus localization**"
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The most likely subcellular site of hs6st3b catalytic action is the Golgi lumen as a type II
membrane protein (family-based inference).
"the most likely subcellular site of hs6st3b catalytic action is the Golgi lumen as a type II membrane protein"
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Recombinant zebrafish Hs6st showed highest activity on N-sulfated heparin-like substrates,
much lower activity on N-acetylated heparin, and essentially no activity on chondroitin,
supporting specificity for HS/heparin-type glycans.
"Recombinant zebrafish Hs6st showed highest activity on N-sulfated heparin-like substrates and much lower activity on N-acetylated heparin; it showed essentially no activity on chondroitin"
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Crystal structures of zebrafish 6-OST show in-line sulfate transfer geometry to the acceptor
6-hydroxyl, with His158 as the catalytic base and Trp210 orienting the acceptor substrate.
"with **His158** positioned as the catalytic base and **Trp210** interacting near the acceptor site to help position the substrate for catalysis"
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Most defensible annotation: hs6st3b is a type II membrane protein that functions in the Golgi
to transfer sulfate from PAPS to the 6-O position of glucosamine residues in HS chains.
"a type II membrane protein expected to function in the **Golgi** to transfer sulfate from **PAPS** to the **6-O position of glucosamine residues** in HS chains"