Guinea pig membrane-bound aminopeptidase P is a member of the proline peptidase family.

Members of the newly recognized proline peptidase family share the ability to hydrolyze imide bonds and share six blocks of highly homologous amino acid sequences. We have found that guinea pig lung and kidney forms of aminopeptidase P, both forms bound to membranes via glycosyl phosphatidylinositol lipid anchors, share at least three of the six conserved blocks of amino acid sequences. In addition, aminopeptidase P acts as an aminoacylproline hydrolase and thus appears to be a member of the proline peptidase family.