This is a family of uncharacterised proteins. The structure of a hypothetical protein from Pseudomonas aeruginosa has shown it to adopt an alpha/beta fold, placing it in the Endonuclease superfamily/clan of restriction endonucleases.

1: Sequence, structure and functional diversity of PD-(D/E)XK phosphodiesterase superfamily. Steczkiewicz K, Muszewska A, Knizewski L, Rychlewski L, Ginalski K; Nucleic Acids Res. 2012;40:7016-7045. PMID:22638584