Abstract
UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (UDP-GlcNAc 2-epimerase) is the key enzyme in the de novo synthesis pathway of neuraminic acid, which is widely expressed as a terminal carbohydrate residue on glycoconjugates. UDP-GlcNAc 2-epimerase is a bifunctional enzyme and catalyzes the first two steps of neuraminic acid synthesis in the cytosol, the conversion of UDP-N-acetylglucosamine to ManAc and the phosphorylation to ManAc-6-phosphate. So far, regulation of this essential enzyme by posttranslational modification has not been shown. Since UDP-N-acetylglucosamine is a cytosolic protein containing eight conserved motifs for protein kinase C (PKC), we investigated whether its enzymatic activity might be regulated by phosphorylation by PKC. We showed that UDP-GlcNAc 2-epimerase interacts with several isoforms of PKC in mouse liver and is phosphorylated in vivo. Furthermore, PKC phosphorylates UDP-GlcNAc 2-epimerase and this phosphorylation results in an upregulation of the UDP-GlcNAc 2-epimerase enzyme activity.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Motifs
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Animals
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Carbohydrate Epimerases / chemistry
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Carbohydrate Epimerases / metabolism
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Cell Line
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Consensus Sequence
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Enzyme Activation / drug effects
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Escherichia coli Proteins*
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Isoenzymes / antagonists & inhibitors
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Isoenzymes / metabolism
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Liver / enzymology*
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Liver / metabolism
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Mice
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Multienzyme Complexes / chemistry
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Multienzyme Complexes / metabolism
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Neuraminic Acids / metabolism
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Phosphorylation / drug effects
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Phosphotransferases (Alcohol Group Acceptor) / chemistry
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Phosphotransferases (Alcohol Group Acceptor) / metabolism*
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Precipitin Tests
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Protein Binding
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Protein Kinase C / antagonists & inhibitors
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Protein Kinase C / metabolism*
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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Spodoptera
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Staurosporine / pharmacology
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Tetradecanoylphorbol Acetate / pharmacology
Substances
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Escherichia coli Proteins
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Isoenzymes
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Multienzyme Complexes
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Neuraminic Acids
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Recombinant Proteins
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Phosphotransferases (Alcohol Group Acceptor)
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N-acylmannosamine kinase
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Protein Kinase C
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Carbohydrate Epimerases
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UDP acetylglucosamine-2-epimerase
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wecB protein, E coli
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Staurosporine
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Tetradecanoylphorbol Acetate