DPP IV has been attributed a large array of functions, some of which are mediated by
its exopeptidase activity. Although it only removes two amino acid residues at the N-terminus
of the peptide, this cleavage can inactivate or modify the activity of regulatory peptides, peptide
hormones, chemokines and neuropeptides. Several excellent DPP IV substrates with high
specificity constants were identified by the in vitro kinetic study of the truncation of bioactive
peptides by DPP IV. In vivo studies e.g.
A Drosophila melanogaster cDNA clone (GH01916)
encoding a putative 723-residue long (82 kDa) protein
(CG 7415) and displaying 50% identity with mammalian
cytosolic dipeptidyl aminopeptidase (DPP) III was func-tionally expressed in Schneider S2
cells. Immunocytochemi-cal studies using anti-(rat liver DPP III) Ig indicated the
expression of this putative DPP III at the outer cell mem-brane and into the cytosol of transfected cells.
X-prolyl dipeptidyl aminopeptidases (X-PDAP) are enzymes catalysing the
release of dipeptides from the amino termini of polypeptides containing a
proline or an alanine at the penultimate position. Involved in various mam-malian regulation processes, as well as in chronic human diseases, they
have been proposed to play a role in pathogenicity forStreptococci.