Functional Characterisation of Two Novel Deacetylases from Streptococcus pyogenes

Streptococcus pyogenes (Group A Streptococcus, GAS) is an exclusively human pathogen that causes a wide range of diseases. We have identified two novel proteins, Spy1094 and Spy1370, which show sequence similarity with peptidoglycan deacetylases (PGDAs) from other streptococcal species like S. pneumoniae and S. iniae, that represent important virulence factors. Recombinant Spy1094 and Spy1370 were active at a wide pH range (pH 4.0–9.0) and showed metal ion-dependence, with the highest activities observed in the presence of Mn2+, Mg2+and Zn2+. The enzymes showed typical Michaelis–Menten saturation kinetics with the pseudo-substrate GlcNAc3. Binding affinities for rSpy1094 and rSpy1370 were high (Km = 2.2 ± 0.9 μM and 3.1 ± 1.1 μM, respectively), but substrate turnover was low (Kcat = 0.0075/s and 0.0089/s, respectively) suggesting that peptidoglycan might not be the preferred target for deacetylation. Both enzymes were expressed during bacterial growth.