Alignment of the mature enzyme regions of PxAP1 and PxAP2 predicted polypeptides with pig pepsin. The numbering system is that of pig pepsin (PepA_PIG) and the vacuolar enzymes from S. cerevisiae (ScPEP4p) and N. crassa (NcPEP4) are included for comparison. The DT/SG and hydrophobic-hydrophobic-Gly motifs forming the psi loops in each domain are boxed, as are the landmark residues Y75 and W39. The Cys residues contributing the three disulphide bonds common to vertebrate APs such as pig pepsin, are shaded and their pairing is indicated by thick () black lines. Gaps introduced to optimise the alignment are indicated by a hyphen.