| Assay Method Information | |
| | P. aeruqinosa LpxC Inhibition Assay |
| Description: | The P. aeruginosa LpxC protein is produced according to the general method of Hyland et al (Journal of Bacteriology 1997 179, 2029-2037: Cloning, expression and purification of UDP-3-O-acyl-GIcNAc deacetylase from Pseudomonas aeruginosa: a metalloamidase of the lipid A biosynthesis pathway). The LC-MS/MS method for quantitation of LpxC product was developed using an Agilent 1200 Capillary HPLC system coupled to an Applied Biosystems MDS Sciex 4000QTRAP mass spectrometer. Both instruments are controlled using the Applied Biosystems MDS Sciex Analyst software. LpxC reaction product (UDP-3-O (R-3-hydroxyacyl)-glucosamine) was produced by hydrolysis of LpxC substrate catalyzed by P.a. LpxC and purified using reversed phase chromatography on a Phenomenex Luna C18(2) 4.6 50 mm column. An LpxC product calibration curve was generated to evaluate the sensitivity and dynamic range of the LC-MS/MS method. Briefly, compounds are pre-incubated with 1 nM P. aeruginosaLpxC for 30 min. at room temperature. Reactions are initiated by the addition of 2 M UDP-3-O (R-3-hydroxydecanoyl)-GIcNAc. Reactions are conducted in a 384-well plate with a total volume of 50 L in each well containing 50 mM Sodium phosphate pH 7.5, 0.005% Trition X-100 for 20 min at room temperature. After quenching with 1.8% HOAc (5 L of a 20% HOAc added to each well), reaction mixtures are analyzed using the LC-MS/MS method and peak areas are transformed into product concentration using a LpxC product calibration curve. Total activity (0% inhibition control) is obtained from reactions with no inhibitors and 100% inhibition control is the background using quenched samples before reaction starts. For IC50 determinations, peak areas are converted to percent inhibition in Microsoft Excel. Percent inhibition values are plotted vs. log compound concentration using XLfit. Data is fit to the four-parameter logistic equation using the non-linear regression algorithm in XLfit to return the IC50 and hill slope values. |
| Affinity data for this assay | |
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