Structural and kinetic differences between the M2 type pyruvate kinases from lung and various tumors

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Pyruvate kinase (PK) is a key glycolytic enzyme.
• PK type M2 is prevalent in tumors and rapidly proliferating cells.
• Understanding PK M2's properties is crucial for cancer research.

Purpose of the Study:

• To compare the kinetic and structural properties of chicken lung and tumor pyruvate kinase type M2.
• To investigate the activation mechanisms of pyruvate kinase M2 by serine and related compounds.
• To identify structural differences between pyruvate kinase types.

Main Methods:

• Purification and characterization of pyruvate kinase from chicken lung and tumors.
• Enzyme kinetics assays with various substrates and effectors (phosphoenolpyruvate, serine, alanine).
• Peptide fragmentation (CNBr-cleavage, V-8 proteolysis) and separation (isoelectric focusing, SDS-PAGE) for structural analysis.

Main Results:

• Chicken tumor pyruvate kinase M2 displayed lower phosphoenolpyruvate affinity, significant serine activation, and strong alanine inhibition compared to lung pyruvate kinase M2.
• Serine activation of chicken lung pyruvate kinase M2 was observed, unlike in rat lung enzyme.
• Structural analysis revealed high homology between lung and tumor PK M2, but identified unique peptide fragments (L, T) characteristic of each type.

Conclusions:

• Chicken pyruvate kinase M2 exhibits distinct kinetic properties in tumors compared to lung tissue, suggesting metabolic adaptation.
• Specific structural features, represented by unique peptide fragments, differentiate PK types.
• These findings contribute to understanding PK M2's role in cancer metabolism and provide targets for drug development.