Structural basis for prolidase deficiency disease mechanisms.

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Prolidase (HsProl) is a metallopeptidase crucial for cleaving iminodipeptides with proline or hydroxyproline residues.
• Prolidase deficiency (PD) is a rare genetic disorder causing severe symptoms due to reduced enzyme activity.
• The structural basis for HsProl inactivation has remained largely unknown.

Purpose of the Study:

• To elucidate the structural basis of human prolidase (HsProl) inactivation caused by PEPD gene mutations.
• To correlate structural changes in HsProl variants with their enzymatic activity.
• To categorize mutation-induced structural alterations and their impact on the enzyme's reaction mechanism.

Main Methods:

• High-resolution crystal structures of multiple human prolidase (HsProl) variants with single amino acid substitutions or deletions were determined.
• The three-dimensional structures were analyzed to understand the implications of mutations.
• Enzymatic activity of the variants was assessed and related to structural findings.

Main Results:

• Four distinct groups of HsProl structural alterations were identified based on their presumed effect on the reaction mechanism.
• Mutations were found to disrupt the catalytic Mn2(OH)-center, cause chain disorder and active site residue displacement, or alter active site rigidity.
• These structural changes provide a mechanistic basis for enzyme inactivation in prolidase deficiency.

Conclusions:

• The study reveals four potential mechanisms of HsProl inactivation at a structural level.
• Understanding these mechanisms is critical for comprehending prolidase deficiency (PD) pathogenesis.
• The findings provide a foundation for developing targeted therapies for PD.