Quantitative spectrophotometric assay for staphylococcal lipase.

Area of Science:

• Microbiology
• Enzymology

Background:

• Staphylococcus aureus produces extracellular lipase, an enzyme with implications in pathogenicity.
• Accurate quantification of lipase activity is crucial for understanding bacterial virulence and developing targeted interventions.

Purpose of the Study:

• To develop and validate a specific spectrophotometric assay for determining lipase activity in Staphylococcus aureus.
• To compare the specificity of the new assay with traditional plate-based methods.

Main Methods:

• Development of a spectrophotometric assay measuring the clearance rate of a tributyrin emulsion.
• Quantification of extracellular lipase produced by S. aureus strains (PS54C, S6C) using purified Pseudomonas lipase as a standard.
• Confirmation of assay specificity using a triolein plate assay and comparison with a tributyrin plate assay.

Main Results:

• The spectrophotometric assay detected as little as 1.0 µg/ml of purified Pseudomonas lipase.
• S. aureus strains PS54C and S6C produced approximately 15 and 60 µg/ml of extracellular lipase, respectively.
• The spectrophotometric assay demonstrated specificity, distinguishing lipase-positive from lipase-negative S. aureus strains, unlike the tributyrin plate assay which showed false positives.

Conclusions:

• A specific and sensitive spectrophotometric assay for quantifying Staphylococcus aureus lipase activity has been developed.
• The developed assay offers superior specificity compared to conventional tributyrin plate assays.
• Kinetic interpretation is essential when using tributyrin-based methods to assess S. aureus lipase activity due to potential lack of specificity.