Aminopeptidase with broad substrate specificity for several peptides. Involved in proteolytic events essential for cell growth and viability. May act as regulator of neuropeptide activity. Plays a role in the antigen-processing pathway for MHC class I molecules. Involved in the N-terminal trimming of cytotoxic T-cell epitope precursors. Digests the poly-Q peptides found in many cellular proteins. Digests tau from normal brain more efficiently than tau from Alzheimer disease brain. Release of an N-terminal amino acid, preferentially alanine, from a wide range of peptides, amides and arylamides. Binds 1 zinc ion per subunit. Strongly inhibited by bestatin, leuhistin, actinonin, amastatin, 1,10-phenanthroline, DFP, PCMBS, Zn(2+), Cd(2+), Co(2+), Cu(2+), Hg(2+), EDTA and puromycin. Not inhibited by PMSF, and only slightly inhibited by leupeptin and aprotinin. Activity is increased by Mg(2+) and Ca(2+). Optimum pH is 7.5. Stable from pH 5.0 to 8.0. Stable up to 40 degrees Celsius. Monomer. Detected in liver, epithelium of renal tubules, epithelium of small and large intestine, gastric epithelial cells, and alveoli of the lung (at protein level). Belongs to the peptidase M1 family. It is uncertain whether Met-1 or Met-45 is the initiator. N-terminal sequencing in PubMed:10978616 suggests that Met-45 is used, followed by methionine initiator removal. Truncated N-terminus. Truncated N-terminus.