Isolation, purification and characterization of pyruvate kinase from Staphylococcus aureus : a potential drug target

Background: With emergence of multidrug-resistant strains of Staphylococcus aureus, there is an urgent need for thedevelopment of new antimicrobials which are narrow and pathogen specific. In this context, pyruvate kinase (PK) an important enzyme in the glycolysis, which catalyses the formation of pyruvate which is the key intersection in thenetwork of metabolic pathways was isolated and purified from Staphylococcus aureus ATCC12600. Methods: Purification steps included 10%-20% ammonium sulphate fractionation, diethyl aminoethyl cellulose ion exchange chromatography followed by gel filtration on Sephadex G-100. The pure PK molecular weight was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Km and Vmax for the PK was demonstrated. Results: The pure PK obtained from Sephadex G-100 gel filtration column exhibited Km of 0.78+0.18 ?M and Vmax 76.47+0.82 ?M NADH/mg/min and molecular weight of 250 kDa in solution. However, in SDS-PAGE showed single band with a molecular weight of 63 kDa confirming the homotetramer nature. In all steps of purification the Km remained constant indicating presence of only one kind of enzyme. The PK gene searched in the genomic sequences of Staphylococcus aureus also confirmed the same. Interpretation and conclusions: In Staphylococcus aureus presence of only one kind of PK unlike in other Gram positive bacteria exhibiting distinct differences in enzyme kinetics. This enzyme also showed the functionality of PK is found to be different from its human host. Therefore, PK probably is regarded as an ideal drug target in the development of new potent antimicrobials.