Immucillin-H, a purine nucleoside phosphorylase transition state analog, causes non-lethal attenuation of growth in Staphylococcus aureus

Purine nucleoside phosphorylase (PNP; EC: 2.4.2.1) is a key enzyme involved in the purine salvage pathway. A recent bioinformatic study by Yadav, P. K. et al. (Bioinformation 2012, 8(14), 664–672) reports PNP as an essential enzyme and potential drug target in community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). We conducted an analysis using the methodology outlined by the authors, but were unable to identify PNP as an essential gene product in CA-MRSA. In addition, the treatment of Staphylococcus aureus cultures with immucillin-H, a powerful inhibitor of PNP, resulted in the non-lethal attenuation of growth, suggesting that PNP activity is not essential for cell viability.