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Nnal has some sequence similarity to metallocarboxypeptidases, but the biochemical characterization of Nnal has not previously been reported. In this work we performed a detailed genomic scan and found >100 Nnal homologues in bacteria, Protista, and Anima‐lia, including several paralogs in most eukaryotic species. Phylogenetic analysis of the Nnal‐like sequences demonstrates a major divergence between Nnal‐like peptidases and the previously known metallocarboxypeptidases subfamilies: M14A, M14B, and M14C. Conformational mod‐eling of representative Nnal‐like proteins from a variety of species indicates an unusually open active site, a property that might facilitate its action on a wide variety of peptide and protein substrates. To test this, we expressed a recombinant form of one of the Nnal‐like peptidases from Caenσrhabditis elegans and demonstrated that this protein is a fully functional …