Falcon deep research report for Danio rerio glceb (D-glucuronyl C5-epimerase B, F1QR43)
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Glce catalyzes C5 epimerization converting D-glucuronic acid (GlcA) to L-iduronic acid (IdoA) within the
heparan sulfate/heparin polymer, increasing chain conformational flexibility important for HS-protein
interactions.
"converts **D-glucuronic acid (GlcA)** residues to **L-iduronic acid (IdoA)** within the polymer"
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Substrate recognition requires N-sulfation context: GLCE preferentially recognizes HS regions where adjacent
glucosamine residues are N-sulfated, coupling epimerization to the modification phase of HS biosynthesis.
"GLCE preferentially recognizes HS regions where adjacent glucosamine residues are **N-sulfated** (GlcNS)"
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The zebrafish Glce crystal structure shows a stable dimer with two catalytic sites per dimer in C-terminal
helical domains; active-site tyrosines Tyr468, Tyr528 and Tyr546 are essential for activity.
"Glce forms a **stable dimer** in which each dimer contains **two catalytic sites** located in C-terminal
helical domains"
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Active-site tyrosines Tyr468, Tyr528 and Tyr546 were shown by structure-guided mutagenesis to be essential
for zebrafish Glce enzymatic activity.
"Tyr468, Tyr528, and Tyr546 were identified as essential for enzymatic activity"
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GLCE is a type II transmembrane Golgi-resident glycan modification enzyme; its HS-modified products act at the
cell surface and ECM after proteoglycan trafficking.
"GLCE/Glce is generally described as a **type II transmembrane protein** in the HS biosynthetic machinery,
which is consistent with function as a Golgi-resident glycan modification enzyme"
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Zebrafish has two Glce paralogs (Glce-A, Glce-B) arising as duplicated orthologs of the single human GLCE
gene, with ~67% and ~73% homology to human GLCE respectively.
"zebrafish were shown to have **two Glce-like paralogs**, **Glce-A and Glce-B**, arising as duplicated
orthologs of the **single human GLCE gene**"
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glce-A and glce-B transcripts are maternally supplied, broadly expressed during gastrulation, and become
restricted by 24 hpf with enrichment in the developing hindbrain.
"both **glce-A and glce-B transcripts are maternally supplied**"
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Overexpression of glce-A or glce-B causes dose-dependent ventralization in zebrafish embryos (smaller head,
expanded blood islands, abnormal somites).
"Overexpression** of glce-A or glce-B causes **dose-dependent ventralization**"
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Morpholino knockdown of glce causes dorsalization (reduced ventral tail fin, kinked/coiled tail, enlarged
heart cavity), resembling reduced BMP signaling.
"Morpholino knockdown** causes **dorsalization**"
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glce activity modulates BMP signaling: overexpression enhances the ventralizing activity of Bmp2b and
knockdown impairs it, linking HS fine structure to BMP-mediated dorsoventral patterning.
"overexpression enhances the ventralizing activity of **Bmp2b**, and knockdown impairs Bmp2b activity"
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Zebrafish Glce was reported to interact with 2-O- and 6-O-sulfotransferases, consistent with a coordinated
'GAGosome' coupling of epimerization with downstream O-sulfation.
"Glce was reported to interact with **2-O- and 6-O-sulfotransferases**"