Leucine Aminopeptidase LAP

Final degradation of substrates to oligopeptides and free amino acids may involve gastro-dermal exopeptidases such as a cathepsin C (Caffrey et al., 2004), which removes dipeptides from the N-terminus of proteins, and a leucine aminopeptidase (LAP McCarthy et al., 2004), which is capable of releasing free amino acids from peptides and dipeptides. However, it is notable that cathepsin B also exhibits carboxydipeptidase activity and, therefore, may well play a dual role (Tort et al., 1999 Caffrey et al., 2004). 

Two-photon fluorescent (TPF) detection, which was initiated by a non-linear optical absorption process, has been performed on a quartz chip. Since the fluorescent efficiency in TPF is inversely proportional to the excitation beam area, the path length dependence problem in fluorescence is significantly reduced. This method is used for analysis of P-naphthylamine (excitation at 580 nm), which is the enzymatic product of leucine aminopeptidase (LAP) acting on the fluorogenic substrate leucine P-naphthylamide [675],... 

Leucine aminopeptidase (LAP, E.C.3.4.11.1) is one of the first discovered and the most widely studied aminopeptidase with respect to sequence, structure and mechanism of action.59 -63 LAP is a zinc containing exopeptidase that catalyzes the removal of amino acids from the N-terminus of peptides or proteins. Similar to other aminopeptidases, this enzyme is of significant biological and medical importance because of its key role in protein modification, activation, and degradation as well as in the metabolism of biologically active peptides and activity regulation of hormonal... 

In general, the best candidates for in vivo assays are extracellular or cell surface associated enzymes because there are a variety of fluorescent or fluorogenic substrates that can be added to intact cells in natural seawater whose disappearance or products can be measured (e.g., leucine aminopeptidases (LAPs), cell surface amino... 

Leucine aminopeptidase (LAP) is a metal-loenzyme that has been inhibited in a slow-binding manner. This exopeptidase catalyzes the hydrolysis of N-terminal amino acids, particularly those with a leucine at the N-termi-nus, although it does have a broad specificity (Equation 17.32). 

These enzymes have been linked here because they have some common applications in diagnostic enzymology. Alanine aminopeptidase (AAP) and leucyl arylamidase (LAAP) hydrolyze the N-terminal amino acids and some amino amides the enzymes respectively hydrolyze leucyl- and alanyl-4-nitroanilide substrates. These enzymes occur in microsomes and are also membrane bound they have been used in studies of both hepatotoxicity and nephrotoxicity. They should not be confused with cytosolic leucine aminopeptidase (LAP) this enzyme is an aminopeptidase that hydrolyzes N-amino acid residues of proteins, in particular those with an N-terminal 1-leucine, where l-leucyl-(3-napthylamide is commonly used as substrate. Urinary alanine aminopeptidase is a useful marker of nephrotoxicity (Jung and Scholz 1980). 

Highly purified leucine aminopeptidase (LAP) from swine kidney (81,157) can liberate amino acids sequentially from the N-terminal... 

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