Interaction of electrically charged lipid monolayers with malate dehydrogenase

Area of Science:

• Biochemistry
• Surface Chemistry
• Enzymology

Background:

• Monomolecular lipid films are crucial models for cell membranes.
• Understanding protein-lipid interactions is key to cellular processes.

Purpose of the Study:

• To investigate the adsorption of malate dehydrogenase onto lipid monolayers.
• To determine how lipid charge and electrolyte composition affect enzyme adsorption and activity.

Main Methods:

• Utilized a multicompartment trough for adsorption studies.
• Varied electrical charge densities of lipid monolayers.
• Modified electrolyte compositions of subphases.

Main Results:

• Closely packed malate dehydrogenase adsorbed onto negatively charged films.
• Significantly less protein adsorbed onto neutral and positively charged films.
• Electrolytes decreased adsorbed protein quantity, and adsorption was irreversible.
• Enzyme activity was low on uncharged films but enhanced by negatively charged lipid headgroups.

Conclusions:

• Lipid film charge density critically influences malate dehydrogenase adsorption.
• Negative surface charge enhances both enzyme adsorption and specific activity.
• Adsorption is irreversible and sensitive to electrolyte concentration.