Presumably involved in the processing and regular turnover of intracellular proteins. Catalyzes the removal of unsubstituted N-terminal amino acids from various peptides (Probable). Possesses leucine aminopeptidase activity against the model substrate leucine-amido methyl coumarin (PubMed:22493451). Possesses Cys-Gly dipeptidase activity. In addition, can cleave Cys-Leu and Leu-Cys dipeptides (PubMed:25716890). Functions as molecular chaperone to protect proteins from heat-induced damage. Release of an N-terminal amino acid, Xaa-|-Yaa-, in which Xaa is preferably Leu, but may be other amino acids including Pro although not Arg or Lys, and Yaa may be Pro. Amino acid amides and methyl esters are also readily hydrolyzed, but rates on arylamides are exceedingly low. Release of N-terminal proline from a peptide. Binds 2 Mn(2+) ions per subunit. Optimum pH is 8.5 for leucine aminopeptidase activity. Homohexamer (dimer of homotrimers). A number of isoforms are produced. According to EST sequences. Belongs to the peptidase M17 family.