Leucyl aminopeptidase
class of enzymes
Leucyl aminopeptidases (EC 3.4.11.1, leucine aminopeptidase, LAPs, leucyl peptidase, peptidase S, cytosol aminopeptidase, cathepsin III, L-leucine aminopeptidase, leucinaminopeptidase, leucinamide aminopeptidase, FTBL proteins, proteinates FTBL, aminopeptidase II, aminopeptidase III, aminopeptidase I) are enzymes that preferentially catalyze the hydrolysis of leucine residues at the N-terminus of peptides and proteins. Other N-terminal residues can also be cleaved, however. LAPs have been found across superkingdoms. Identified LAPs include human LAP, bovine lens LAP, porcine LAP, Escherichia coli (E. coli) LAP (also known as PepA or XerB), and the solanaceous-specific acidic LAP (LAP-A) in tomato (Solanum lycopersicum).
Enzyme description, structure, and active site
The active sites in PepA and in bovine lens LAP have been found to be similar. Shown in the picture below is the proposed model for the active site of LAP-A in tomato based on the work of Strater et al. It is also known that the biochemistry of the LAPs from these three kingdoms is very similar. PepA, bovine lens LAP, and LAP-A preferentially cleave N-terminal leucine, arginine, and methionine residues. These enzymes are all metallopeptidases requiring divalent metal cations for their enzymatic activity Enzymes are active in the presence of Mn+2, Mg+2 and Zn+2. These enzymes are also known to have high pH (pH 8) and temperature optima.
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