Seven pyruvate kinase variants characterized by the ICSH recommended methods

Area of Science:

• Biochemistry
• Hematology
• Genetics

Background:

• Pyruvate kinase (PK) deficiency is a genetic disorder causing chronic hemolytic anemia.
• Understanding novel PK variants is crucial for diagnosing and managing hemolytic anemias.

Purpose of the Study:

• To characterize seven new red-cell pyruvate kinase (PK) variants found in Japanese individuals.
• To elucidate the molecular mechanisms underlying defective PK function in these variants.

Main Methods:

• Characterization of novel PK variants using International Committee for Standardization in Haematology (ICSH) recommended methods.
• Analysis of enzyme kinetics, including substrate affinity (K0.5S for phosphoenolpyruvate) and thermal stability.
• Assessment of product inhibition by ATP.

Main Results:

• Seven novel Japanese PK variants (PK Tokyo, Nagasaki, Sapporo, Maebashi, Itabashi, Fukushima, Aizu) were identified in true homozygotes.
• Low substrate affinity and thermal instability were identified as major contributors to defective PK function.
• Product inhibition by ATP was found to contribute to hemolysis in over half of the cases.

Conclusions:

• The identified PK variants lead to chronic hemolytic anemia primarily through impaired enzyme kinetics and stability.
• These findings expand the spectrum of known PK deficiency-causing mutations.
• Further research into PK variants can improve diagnostic accuracy and therapeutic strategies for hemolytic anemias.