5.1.4 Aminopeptidases and Arylamidases
These enzyme assays have been linked here as they have some common applications in
diagnostic enzymology.
Alanine aminopeptidase (AAP) and leucine arylamidase (LAAP) hydrolyse peptides
at the N-terminal amino acid and some amino acid amides; the enzymes respectively
hydrolyse leucyl- and alanyl-4-nitroanilide substrates. They occur in microsomes and are
also membrane bound, and they have been used in studies of both hepatotoxicity and
nephrotoxicity. These two enzymes should not be confused with cytosolic leucine
aminopeptidase (LAP): this enzyme is an aminopeptidase which hydrolyses N-amino
acid residues of proteins, in particular those with an N-terminal 1-leucine where 1-leucyl-
β-napthylamide is commonly used as substrate.