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Updated: Aug 16, 2026

Identification of Kinase-substrate Pairs Using High Throughput Screening
Published on: August 29, 2015
Protein kinase C phosphorylates and regulates UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase
R Horstkorte1, S Nöhring, K Danker
1Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-14195, Berlin-Dahlem, Germany. rhorstko@zedat.fu-berlin.de
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.
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