ABSTRACT
Aminopeptidases catalyze the hydrolysis of amino acid residues from the amino terminus of protein or peptide substrates. Widely distributed in many types of tissues, they are found on the cell surface, in the cytoplasm or in soluble secreted forms, and they are evolutionarily conserved. Most of the aminopeptidases have been found in mammalian and bacterial cells. Many, if not all, are metallopeptidases in that they require Zn2 + or other metal ions for their enzymatic activity. The aminopeptidases have a variety of functions. They are involved in protein maturation, activation or degradation of regulatory peptides, and scavenging proteolytic peptides for nutritional purposes. With the identification of the BP-1/6C3 antigen on lymphoid cells as glutamyl aminopeptidase (aminopeptidase A) and the CD13 antigen on myeloid cells as membrane alanyl aminopeptidase (aminopeptidase N), convergent evidence has accumulated that these aminopeptidases, along with other ectoenzymes, may serve not just as enzymatic markers of cell differentiation or leukaemic transformation, but may also be involved in cell adhesion, signal transduction and viral cell entry, as well as in the regulation of hormonal and non-hormonal peptides.
