PA_SaNapH_like: Protease-associated domain containing proteins like Streptomyces anulatus N-acetylpuromycin N-acetylhydrolase (SaNapH).This group contains various PA domain-containing proteins similar SaNapH. Proteins in this group belong to the peptidase M28 family. NapH is a terminal enzyme in the puromycin biosynthetic pathway; NapH hydrolyzes N-acetylpuromycin to the active antibiotic. The significance of the PA domain to these proteins has not been ascertained. It may be a protein-protein interaction domain. At peptidase active sites, the PA domain may participate in substrate binding and/or promoting conformational changes, which influence the stability and accessibility of the site to substrate.