Conformational Change and Activity Enhancement of Rabbit Muscle Lactate Dehydrogenase Induced by Polyethyleneimine

Area of Science:

• Biochemistry
• Protein-polymer interactions
• Enzyme kinetics

Background:

• Polyethyleneimine (PEI) is a cationic polymer with diverse applications.
• Understanding PEI's interaction with proteins is crucial for its use in biological systems.
• Rabbit muscle lactate dehydrogenase (rmLDH) is a key enzyme in cellular metabolism.

Purpose of the Study:

• To investigate the interaction between PEI and rmLDH.
• To elucidate how PEI binding affects rmLDH conformation and bioactivity.
• To determine the influence of PEI molecular weight on these effects.

Main Methods:

• Spectroscopic techniques including UV-vis absorption, resonance Rayleigh scattering, fluorescence, and circular dichroism.
• Assays to measure enzyme activity and binding efficiency.
• Varying PEI molecular weights were used.

Main Results:

• PEI binds to rmLDH via hydrogen bonding and hydrophobic interactions, overcoming electrostatic repulsion.
• PEI binding reduces the efficiency of rmLDH binding to its coenzyme and substrate.
• Complex formation with PEI induces conformational changes, increases surface hydrophobicity, and enhances rmLDH catalytic activity.
• Higher molecular weight PEI demonstrates a more pronounced effect on rmLDH conformation and activity.

Conclusions:

• PEI can modulate the structure and function of rmLDH.
• The interaction is complex, involving both inhibitory and activating effects on enzyme activity.
• PEI's molecular weight is a critical factor in determining the extent of rmLDH alteration.