Aminopeptidases are a group of enzymes widely distributed among bacteria, fungi, animals and plants that catalyze the cleavage of amino acids from the amino terminus of protein or peptide substrates through hydrolysis of peptide bonds near the N-terminal end of a polypeptide chain.  Most aminopeptidases are assembled by relatively high mass (50kDa) subunits exhibiting multimeric structures, whereas some are monomeric. The majority of aminopeptidases are zinc metalloenzymes and hence inhibited by the transition-state analog bestatin.  Aminopeptidases have been found in many subcellular organelles as well as in cytoplasm and membrane, where they are involved in diverse proteolytic pathways and play an essential role in protein maturation, degradation of non-hormonal and hormonal peptides and possibly determination of protein stability.