The protein tyrosine phosphatase from Streptococcus pyogenes, SP-PTP, is an important regulatory protein in this human pathogen. Studies have shown that SP-PTP regulates as much as 50% of genes involved in virulence of S. pyogenes. Because of this, it is important to study its function and interaction with potential inhibitors. Recombinant SP-PTP was expressed in E. coli and purified through affinity and size exclusion chromatography. The phosphatase activity was characterized using a synthetic substrate, para-nitrophenylphosphate. Kinetics parameters were determined by monitoring the production of dephosphorylated substrate. Inhibition by known protein tyrosine phosphatase, sodium orthovanadate, was also characterized. SP-PTP shares a very similar structure with the human low molecular weight protein tyrosine phosphatase, LMW-PTP. As only the open conformations of both are currently available, a vanadate-bound structure will reveal more about the mechanisms of both proteins. Finally, LMW-PTP inhibitors will also be characterized for their potential ability to inhibit SP-PTP.
