This entry represents the C-terminal domain of 6-phospho-N-acetylmuramidase (MupG) found in bacteria. It characterises putative phospho sugar glycosidases found in Gram-negative and -positive species, but mainly in firmicutes. MupG from Staphylococcus aureus [1], specifically cleaves MurNAc 6P-GlcNAc, a product of cell wall turnover, into the sugars MurNAc 6P and GlcNAc, being involved in cell wall turnover and recycling. Since some species, for example Lactobacillus plantarum, possess several putative paralogs, the substrate specificity of these proteins may not be limited to cell wall sugars, but may include phosphorylated disaccharides in general. Most proteins containing this domain appear to consist of two structural subdomains, as it can be seen in the two available crystal structures of Enterococcus faecalis (PDB:2p0o) and Bacillus cereus (PDB:1X7F). The larger N-terminal domain constitutes a TIM-barrel like structure and the C-terminal domain (this entry) is similar to the cyclophilin family. It should be noted that some proteins lack this domain.

1: Recovery of the Peptidoglycan Turnover Product Released by the Autolysin Atl in Staphylococcus aureus Involves the Phosphotransferase System Transporter MurP and the Novel 6-phospho-N-acetylmuramidase MupG. Kluj RM, Ebner P, Adamek M, Ziemert N, Mayer C, Borisova M; Front Microbiol. 2018;9:2725. PMID:30524387