Bound hydroxyproline excretion following gelatin loading in prolidase deficiency

Area of Science:

• Biochemistry
• Human Physiology
• Genetics

Background:

• Prolidase is an enzyme crucial for the hydrolysis of dipeptides containing proline.
• Deficiency in prolidase leads to an accumulation of peptide-bound hydroxyproline.
• Understanding hydroxyproline metabolism is important for diagnosing and managing related disorders.

Purpose of the Study:

• To evaluate peptide-bound hydroxyproline excretion in individuals with prolidase deficiency and heterozygotes.
• To assess the impact of gelatin loading on hydroxyproline excretion in different subject groups.
• To elucidate the role of prolidase in the intestinal absorption and hydrolysis of hydroxyproline.

Main Methods:

• Assessing peptide-bound hydroxyproline excretion before and after gelatin loading.
• Comparing excretion patterns in children and adults with prolidase deficiency, heterozygotes, and normal controls.
• Quantifying the ingested hydroxyproline load and its subsequent excretion over 24 hours.

Main Results:

• Prolidase deficiency patients excreted 6.9-24 times more bound hydroxyproline than controls.
• Following gelatin loading, homozygotes excreted 14.4-17.3 times more ingested hydroxyproline than normal children.
• A significant portion of ingested hydroxyproline was excreted unhydrolyzed in prolidase deficiency patients.

Conclusions:

• Prolidase deficiency leads to substantial unhydrolyzed peptide-bound hydroxyproline crossing the intestinal wall.
• Prolidase plays a vital role in the normal hydrolysis of peptide-bound hydroxyproline.
• The study underscores the diagnostic utility of hydroxyproline excretion tests in prolidase deficiency.