These peptidases are found in Archaea and Bacteria. The example in Lactococcus lactis, PepA, aids growth on milk [1]. Pyrococcus horikoshii contain a thermostable de-blocking aminopeptidase member of this family used commercially for N-terminal protein sequencing [2].

1: A non-essential glutamyl aminopeptidase is required for optimal growth of Lactococcus lactis MG1363 in milk. l'Anson KJ, Movahedi S, Griffin HG, Gasson MJ, Mulholland F; Microbiology 1995;141:2873-2881. PMID:8535515

2: Active site of deblocking aminopeptidase from Pyrococcus horikoshii. Onoe S, Ando S, Ataka M, Ishikawa K; Biochem Biophys Res Commun 2002;290:994-997. PMID:11798173

3: Thermostable aminopeptidase from Pyrococcus horikoshii. Ando S, Ishikawa K, Ishida H, Kawarabayasi Y, Kikuchi H, Kosugi Y; FEBS Lett 1999;447:25-28. PMID:10218575

4: Tetrahedral aminopeptidase: a novel large protease complex from archaea. Franzetti B, Schoehn G, Hernandez JF, Jaquinod M, Ruigrok RW, Zaccai G; EMBO J 2002;21:2132-2138. PMID:11980710