puromycin-sensitive aminopeptidase; PSA; cytosol alanyl aminopeptidase; arylamidase AAP-S (NPEPPS, PSA)

^[1]^[2]

Function

aminopeptidase with broad substrate specificity for several peptides
role in proteolytic events essential for cell growth & viability
may act as regulator of neuropeptide activity
role in the antigen-processing pathway for MHC class I molecules
role in N-terminal trimming of cytotoxic T-cell epitope precursors
digests the polyglutamine tract 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 & arylamides
activity is increased by Mg+2 & Ca+2

Cofactor: binds 1 Zn+2 per subunit (putative)

Inhibition:

strongly inhibited by bestatin, leuhistin, actinonin, amastatin, 1,10-phenanthroline, DFP, PCMBS, Zn+2, Cd+2, Co+2, Cu+2, Hg+2, EDTA & puromycin
not inhibited by PMSF
only slightly inhibited by leupeptin & aprotinin

expressed in liver
expressed in epithelium (at protein level) of:
- renal tubules
- stomach, small intestine, colon
- alveoli of the lung

uncertain whether Met-1 or Met-45 is the initiator
N-terminal sequencing suggests that Met-45 is used, followed by removal of the initiator methionine