Structural and functional study of D-glucuronyl C5-epimerase

Area of Science:

• Biochemistry
• Structural Biology
• Glycoscience

Background:

• Heparan sulfate (HS) is a critical glycosaminoglycan involved in numerous physiological processes.
• D-glucuronyl C5-epimerase (Glce) catalyzes a key modification in HS biosynthesis, enhancing its functional diversity.

Purpose of the Study:

• To elucidate the structural basis of Glce activity and product inhibition.
• To understand the role of specific active site residues in Glce function.

Main Methods:

• X-ray crystallography to determine Glce structures in apo-form and complex with heparin hexasaccharide.
• Site-directed mutagenesis to investigate the function of key active site residues.

Main Results:

• Crystal structures revealed Glce exists as a stable dimer with two catalytic sites.
• Three active site tyrosine residues (Tyr468, Tyr528, Tyr546) were identified as crucial for enzymatic activity.
• The mechanism of product inhibition was elucidated, involving sulfation patterns shielding the C5 carbon.

Conclusions:

• Structural and functional data provide key insights into Glce-mediated HS modification.
• Understanding Glce mechanism advances knowledge of HS biosynthesis and its regulation.