In vivo processing of Staphylococcus aureus lipase

Area of Science:

• Microbiology
• Enzymology
• Protein Biochemistry

Background:

• The Staphylococcus aureus lipase gene (geh) encodes a 76-kDa protein.
• Purified extracellular lipase typically appears as a 45- to 46-kDa protein.

Purpose of the Study:

• To investigate the in vivo secretion and processing of Staphylococcus aureus lipase.
• To identify the molecular weight of the secreted lipase and its mature form.
• To understand the mechanism and consequences of lipase post-translational modification.

Main Methods:

• In vivo secretion analysis of Staphylococcus aureus lipase.
• Purification and enzymatic activity assays of lipase forms.
• Protein sequencing to determine cleavage sites and identify processing enzymes.

Main Results:

• Staphylococcus aureus lipase is secreted as an 82-kDa active prolipase.
• The 82-kDa prolipase undergoes sequential processing to a mature 45- to 46-kDa enzyme.
• Protein sequencing revealed cleavage of a 295-amino acid N-terminal region, leaving the active site-containing core intact.
• A metallocysteine protease is implicated in initiating the processing cascade.
• The mature lipase is hydrophobic, protease-resistant, and retains full catalytic activity.

Conclusions:

• Staphylococcus aureus lipase undergoes significant post-translational processing from an 82-kDa prolipase to a 45-kDa mature enzyme.
• This processing is essential for generating the active, secreted form of the lipase.
• The mature lipase's stability and retained activity suggest an important role in S. aureus pathogenesis or extracellular functions.