Related Experiment Videos
Control of glycoprotein synthesis
The Journal of Biological Chemistry
|May 25, 1983
Summary
This study identifies UDP-GlcNAc:GnGn (GlcNAc to Man alpha 1-3) beta 4-N-acetylglucosaminyltransferase IV (GlcNAc-transferase IV) in hen oviduct membranes. This enzyme is crucial for forming triantennary oligosaccharides, with specific substrate requirements for optimal activity.
Area of Science:
- Glycobiology
- Enzymology
- Biochemistry
Background:
- Oviduct membranes catalyze oligosaccharide synthesis.
- UDP-GlcNAc:GnGn beta 4-N-acetylglucosaminyltransferase IV (GlcNAc-transferase IV) is a key enzyme in this process.
- Distinguishing GlcNAc-transferase IV from other oviduct enzymes is important for understanding glycosylation pathways.
Purpose of the Study:
- To identify and characterize GlcNAc-transferase IV in hen oviduct membranes.
- To elucidate the substrate specificity of GlcNAc-transferase IV.
- To compare GlcNAc-transferase IV activity across different species and tissues.
Main Methods:
- Enzyme assays using UDP-GlcNAc and a specific oligosaccharide substrate.
- Separation of enzyme products using concanavalin A/Sepharose chromatography.
- Structural characterization of products via proton NMR spectroscopy and methylation analysis.
Main Results:
- GlcNAc-transferase IV activity was quantified in hen oviduct membranes (7 nmol/mg/h).
- The enzyme primarily produces triantennary oligosaccharides, with some bisected triantennary material also formed.
- Maximal activity requires specific terminal GlcNAc residues; modifications like galactose reduce activity significantly.
Conclusions:
- GlcNAc-transferase IV plays a vital role in synthesizing triantennary structures in hen oviducts.
- The enzyme exhibits strict substrate specificity, influenced by terminal sugar residues.
- Similar GlcNAc-transferase IV activities were observed in rat liver and pig thyroid membranes, suggesting conserved functions.