Functional Changes of Lysozyme by Conjugating with Carboxymethyl Dextran

Area of Science:

• Biochemistry
• Materials Science
• Protein Engineering

Background:

• Protein modification is crucial for enhancing protein functionality and stability.
• Acidic polysaccharides can be used to create novel protein conjugates.
• Hen egg lysozyme (HEL) is a model enzyme for studying protein modifications.

Purpose of the Study:

• To prepare a hen egg lysozyme-carboxymethyl dextran (HEL-CMD) conjugate.
• To investigate the impact of conjugation on HEL's enzymatic activity, stability, and conformation.
• To establish a model for protein-acidic polysaccharide conjugation.

Main Methods:

• Conjugation of HEL with CMD using water-soluble carbodiimide.
• Confirmation of acid-amide bond formation via SDS-PAGE, isoelectric focusing, and IR spectroscopy.
• Assessment of enzymatic activity, thermal stability, and conformational changes (α-helix content) using spectroscopic techniques.

Main Results:

• A HEL-CMD conjugate with a 1:1 molar ratio was successfully synthesized.
• The conjugate exhibited altered enzymatic activity, with higher activity at extreme temperatures (4°C, 80°C) and retained 60% activity at moderate temperatures (40-60°C).
• Conjugation led to a decrease in α-helix content but maintained overall thermal stability, with increased resistance to proteolysis.

Conclusions:

• The HEL-CMD conjugate demonstrates modified functional properties compared to native HEL.
• This study provides a viable method for creating protein-polysaccharide conjugates with tailored characteristics.
• The findings suggest potential applications for such conjugates in areas requiring enhanced protein stability and controlled activity.