Phospholipase D modified with a polyethylene glycol derivative.

Area of Science:

• Biochemistry
• Enzymology
• Protein Modification

Background:

• Phospholipase D (PLDP) from Streptomyces sp. AA586 is an enzyme with hydrolytic and transphosphatidyl activities.
• Protein modification techniques are crucial for altering enzyme properties for various applications.

Purpose of the Study:

• To investigate the effects of methoxypolyethylene glycol succinimidylsuccinate (ss-PEG) modification on the properties of PLDP.
• To assess changes in enzyme stability, molecular weight, and catalytic activity post-modification.

Main Methods:

• PLDP was modified using ss-PEG, a polyethylene glycol derivative.
• Trinitrobenzene sulfonate (TNBS) titration was used to quantify the extent of amino group modification.
• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration (Toyopearl HW-55F) assessed molecular weight changes.
• High-performance liquid chromatography (HPLC) with CM-Toyopearl evaluated changes in charge properties.
• Enzyme stability (thermal and pH) and kinetic parameters (Km) were determined.

Main Results:

• Approximately 70% of PLDP's free amino groups were modified by ss-PEG.
• PEGylation increased the enzyme's molecular weight and reduced its cationic charge, leading to faster elution in HPLC.
• Modified PLDP exhibited significantly enhanced thermostability without changes in pH stability or optimal pH.
• The Michaelis constant (Km) for phosphatidylcholine in the hydrolytic reaction doubled, while Km for the transphosphatidyl reaction remained largely unchanged.

Conclusions:

• ss-PEG modification effectively alters PLDP's physicochemical properties, notably enhancing its thermal stability.
• PEGylation influences enzyme kinetics, increasing the Km for hydrolysis but not significantly affecting transphosphatidylation.
• This modification strategy holds potential for improving enzyme performance in biotechnological applications requiring enhanced stability.