Peptide deformylase as an antibacterial drug target: Target validation andresistance development

New inhibitors of peptide deformylase (PDF) which are very potent against t he isolated enzyme and show a certain degree of antibacterial activity have recently been synthesized by our group. Several lines of experimental evid ence indicate that these inhibitors indeed interfere with the target enzyme in the bacterial cell. (i) The inhibition of Escherichia coli growth could be counteracted by overexpression of PDF from different organisms, includi ng E. coli, Streptococcus pneumoniae, and Haemophilus influenzae. Conversel y, reduced expression of PDF in S. pneumoniae resulted in an increased susc eptibility to the inhibitors. (ii) Proteome analysis on two-dimensional gel s revealed a shift for many proteins towards lower pi in the presence of PD F inhibitors, as would be expected if the proteins still carry their N-form yl-Met terminus. (iii) PDF inhibitors show no antimicrobial activity agains t E, coli under conditions that make growth independent of formylation and deformylation, The antibacterial activity in E, call was characterized as b acteriostatic, Furthermore, the development of resistance in E, coil was ob served to occur with high frequency (10(-7)). Resistant mutants show a redu ced growth rate, and DNA sequence analysis revealed mutations in their form yl transferase gene. Taking all these aspects into account, we conclude tha t PDF may not be an optimal target for broad-spectrum antibacterial agents.