The Non-phosphorylating Glyceraldehyde-3-Phosphate Dehydrogenase GapN Is a Potential New Drug Target in Streptococcus pyogenes

          The strict human pathogen
          Streptococcus pyogenes
          causes infections of varying severity, ranging from self-limiting suppurative infections to life-threatening diseases like necrotizing fasciitis or streptococcal toxic shock syndrome. Here, we show that the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase GapN is an essential enzyme for
          S. pyogenes
          . GapN converts glyceraldehyde 3-phosphate into 3-phosphoglycerate coupled to the reduction of NADP to NADPH. The knock-down of
          gapN
          by antisense peptide nucleic acids (asPNA) significantly reduces viable bacterial counts of
          S. pyogenes
          laboratory and macrolide-resistant clinical strains
          in vitro
          . As
          S. pyogenes
          lacks the oxidative part of the pentose phosphate pathway, GapN appears to be the major NADPH source for the bacterium. Accordingly, other streptococci that carry a complete pentose phosphate pathway are not prone to asPNA-based
          gapN
          knock-down. Determination of the crystal structure of the
          S. pyogenes
          GapN apo-enzyme revealed an unusual cis-peptide in proximity to the catalytic binding site. Furthermore, using a structural modeling approach, we correctly predicted competitive inhibition of
          S. pyogenes
          GapN by erythrose 4-phosphate, indicating that our structural model can be used for
          in silico
          screening of specific GapN inhibitors. In conclusion, the data provided here reveal that GapN is a potential target for antimicrobial substances that selectively kill
          S. pyogenes
          and other streptococci that lack the oxidative part of the pentose phosphate pathway.