Structure and function of normal and variant human phosphoglycerate kinase

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Human phosphoglycerate kinase (PGK) is a crucial enzyme in glycolysis.
• Genetic variations in PGK can lead to enzyme deficiency and associated health issues.
• Understanding PGK structure-function relationships is vital for diagnosing and treating related disorders.

Purpose of the Study:

• To determine the complete amino acid sequence of normal human phosphoglycerate kinase (PGK).
• To investigate the structural abnormalities and functional consequences of PGK variants (PGK-II and PGK-München).
• To elucidate the role of specific amino acid residues in enzyme stability and activity.

Main Methods:

• Amino acid sequencing to determine the primary structure of normal human PGK.
• Analysis of variant PGK enzymes (PGK-II and PGK-München) to identify amino acid substitutions.
• Enzyme activity assays and stability tests (e.g., heat instability) to assess functional impact.
• Citrate binding studies for variant enzymes.

Main Results:

• The normal human PGK enzyme comprises 417 amino acid residues.
• PGK-II variant shows a threonine to asparagine substitution at position 352, altering citrate binding without affecting enzyme activity.
• PGK-München variant exhibits an aspartic acid to asparagine substitution at position 267, leading to reduced enzyme activity (20% of normal) and heat instability.
• The negative charge of aspartic acid at position 267 is critical for maintaining PGK enzyme stability.

Conclusions:

• The complete amino acid sequence of human PGK has been established.
• Specific amino acid substitutions in PGK can significantly alter enzyme stability and function.
• The findings provide insights into the molecular basis of hereditary PGK deficiency and associated hemolysis, highlighting the importance of residue 267 for enzyme stability.