Interaction between tissue transglutaminase and phospholipid vesicles

Area of Science:

• Biochemistry
• Membrane Biophysics
• Enzymology

Background:

• Phospholipid vesicles are model systems for cell membranes.
• Transglutaminases are enzymes involved in protein cross-linking.
• Enzyme-membrane interactions are crucial for cellular processes.

Purpose of the Study:

• To investigate the interaction between liver transglutaminase and phospholipid vesicles.
• To determine the conditions under which this interaction occurs.
• To understand the effect of the interaction on enzyme activity and vesicle integrity.

Main Methods:

• Small unilamellar phospholipid vesicles were prepared.
• Purified liver transglutaminase was incubated with vesicles.
• Carboxyfluorescein release assay was used to measure encapsulation.
• Sepharose 4B chromatography was employed to analyze enzyme-vesicle complexes.
• Enzyme activity assays were performed.

Main Results:

• A specific interaction between liver transglutaminase and phospholipid vesicles was observed at the lipid phase transition.
• Enzyme-induced bilayer perturbation led to the release of encapsulated carboxyfluorescein.
• The size of enzyme-phospholipid complexes varied with the protein-phospholipid ratio.
• Transglutaminase activity was significantly reduced upon insertion into the vesicle bilayer.
• Interaction was dependent on the vesicle's lipid phase and the enzyme's structural integrity.

Conclusions:

• Liver transglutaminase interacts specifically with phospholipid bilayers at their phase transition.
• This interaction perturbs the membrane, causing release of encapsulated contents.
• The enzyme's activity is diminished when integrated into the lipid bilayer.
• The findings provide insights into enzyme-membrane dynamics and potential mechanisms of drug delivery or membrane modification.