The enzyme is found in bacterial membranes and in chloroplast thylakoid membranes. Unaffected by inhibitors of most serine peptidases, but site-directed mutagenesis implicates a Ser/Lys catalytic dyad in activity [1,3]. Hydrolyses a single bond -Ala!Ala- in M13 phage procoat protein, producing free signal peptide and coat protein. Formerly included in EC
3.4.99.36. Eukaryote signal peptidases that may have somewhat different specificity are known from the endoplasmic reticulum membrane [4] and mitochondrial inner membrane [2]. Type example of peptidase family S26
