Human hypoxanthine phosphoribosyltransferase. Purification and properties

Area of Science:

• Biochemistry
• Enzymology
• Human Physiology

Background:

• Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is crucial for purine metabolism.
• Deficiency in HGPRT causes Lesch-Nyhan syndrome, a severe neurological disorder.
• Understanding HGPRT's properties is vital for metabolic research.

Purpose of the Study:

• To purify and characterize hypoxanthine phosphoribosyltransferase (HPRT) from human erythrocytes.
• To determine the enzyme's physical and chemical properties.

Main Methods:

• Enzyme purification using multiple chromatography steps.
• Analytical ultracentrifugation (sedimentation coefficient and equilibrium).
• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
• Isoelectric focusing.
• Amino acid composition analysis.

Main Results:

• HPRT was purified 13,000-fold to homogeneity from human erythrocytes.
• Native enzyme molecular weight: 81,000-83,000 Da; sedimentation coefficient: 5.9 S.
• SDS-PAGE indicated a subunit molecular weight of 26,000 Da, suggesting a trimeric structure.
• Isoelectric focusing revealed three activity peaks at pH 5.6, 5.7, and 5.9.
• Detailed amino acid composition was determined; the N-terminus appears blocked.

Conclusions:

• The study successfully purified and characterized human erythrocyte HPRT.
• The enzyme is a trimer with specific biophysical properties.
• These findings provide a foundation for further structural and functional studies of HPRT.