Kidney leucine aminopeptidase

Porcine kidney leucine aminopeptidase also binds one Zn2+ per subunit, which is essential for catalysis. The activity of the enzyme is regulated by the binding of divalent metal ions at a second site. 

In related work, Dong and Martin developed an assay that detects the catalytic activity of the enzymes pig liver esterase and porcine kidney leucine aminopeptidase by using substrates which have been labeled with metal-binding ligands [57], The enzymes catalyze changes in the substrates that affect their ability to bind to non-luminescent Ru complexes to form mixed-ligand complexes capable of ECL. 

A Taylor, T Surgenor, DK Thomson, RJ Graham, H Oettgen (1984) Comparison of leucine aminopeptidase from human lens, beef lens and kidney, and hog lens and kidney, Exp Eye Res 38 217-229... 

Aminopeptidases are present in many tissues (Table III). Leucine aminopeptidase from intestinal mucosa is very effective in catalyzing the hydrolysis of leucine from the amino terminus of peptides, polypeptides, and proteins. It also hydrolyzes leucine amide and leucine esters (10). The designation leucine aminopeptidase is somewhat of a misnomer because activity is also observed when other amino acids replace leucine. Only the L-isomers of amino acids are substrates, and the presence of a D-amino acid residue or proline in the penultimate position will retard hydrolysis (10). Enzymes having the same specificity as the intestinal aminopeptidase have been identified and/or isolated from kidney, pancreas, muscle, lens, and various bacterial sources (10). The kidney... 

The first evidence indicating that leucine aminopeptidase is a metallo-enzyme was obtained only recently (20, 21) although metals have long been known to aflfect its activity (22). Both the lens and the kidney... 

The specificity of this enzyme from swine kidney has been established from detailed studies with synthetic substrates (reviewed by Smith and Hill, 1960). All peptide bonds formed by L-amino acids which are adjacent to a free a-amino group are susceptible to hydrolysis, although the rates of hydrolysis vary over a several thousandfold range. The best substrates are those which contain amino-terminal leucine and the poorest are those which contain the amino nitrogen of proline in peptide linkage, e.g., glycyl-proline (Hill and Schmidt, 1962). The action of leucine aminopeptidase on protein and polypeptide substrates (Hill and Smith, 1958, 1959) agrees with the specificity established with synthetic substrates. 

Leucine arylamidase (= leucine aminopeptidase) is a ubiquitous enzyme, mainly localized in the liver and bile ducts as well as in the pancreas, breast, intestine and kidney. During pregnancy (as from trimester), LAP increases. Arylamidases are predominantly localized in the cytoplasm, while aminopeptidases are found in the microsomes of hepatocytes. LAP splits aminoterminal amino acids off from peptides. High LAP activities are detectable in the epithelia of the bile ducts. 

Leucine aminopeptidase Hepatobiliary system, intestine, pancreas, kidney... 

Measurement of serum y-GT activity has clinical significance. The enzyme is present in all tissues, but the highest level is in the kidney however, the serum enzyme originates primarily from the hepatobiliary system. Elevated levels of serum y-GT are found in the following disorders intra- and posthepatic biliary obstruction (elevated serum y-GT indicates cholestasis, as do leucine aminopeptidase, 5 -nucleotidase, and alkaline phosphatase) primary or disseminated neoplasms some pancreatic cancers, especially when associated with hepatobiliary obstruction alcohol-induced liver disease (serum y-GT may be exquisitely sensitive to alcohol-induced liver injury) and some prostatic carcinomas (serum from normal males has 50% higher activity than that of females). Increased activity is also found in patients receiving phenobarbital or phenytoin, possibly due to induction of y-GT in liver cells by these drugs. 

Leucine aminopeptidase Porcine kidney 300,000 6 N-terminal exopeptidase Zn binds at two sites, one for catalysis, the other for regulation. 

Leucine aminopeptidase EC 3.4.11.1 Leu-X- (AA-X-) Bovine and pig lens and kidney Activated by Mg, Mn basic pH optimum chromogenic substrates not hydrolysed inhib. by 1,10 phenanthroline, acti-nonin, bestatin 6 subunits of M, 53000. 

Leucine aminopeptidase preferentially hydrolyses peptide bonds adjacent to an Al-terminal residue that carries a large hydrophilic side chain, in particular a leucyl residue. Commonly used synthetic substrates are leucinamide, leucine 4-nitroanilide and leucine hydrazide. This cytosolic zinc-metalloenzyme has been identified in virtually all animal tissues, and most studies have been performed on the enzyme (Mj 324,000) from bovine lens, which has been crystallized. It consists of 6 identical subunits (M, 54,000 487 amino acids 2 Zrf per subunit), and its catalytically active site is in the C-terminal domain. The enzyme is present in many other cells and tissues, e.g. lung, stomach, kidney intestine, serum and leukocytes. In clinical chemistry, this enzyme is a marker for hepatic cell lysis, and may even be a more sensitive marker for acute hepatitis than the aminotransferases. 

Leucine Aminopeptidase, Leucine aminopeptidase was named at a time when only a few authentic peptides were available for study. The ability of intestinal preparations to split peptides containing N-terminal leucine was shown by Linderstr0m-Lang in 1929, and the enzyme responsible was partially purified by Johnson el dJ in 1936. The purified enzyme requires a divalent cation, Mg++ or Mn++, for activity. The properties of this enzyme have been studied extensively by Smith and his collaborators. They have found that the corresponding activity in hog kidney can be purified more highly than the best preparations obtained from intestinal mucosa. The properties described below are for the hog kidney enzyme, but the corresponding enzymes from other sources appear to have similar properties. 

Cathepsins. Cathepsins are intracellular proteases of animal origin. The occurrence of several such enzymes has been demonstrated in various tissues, including spleen, pituitary gland, kidney, thymus, etc. It is obvious that there is no reason to anticipate that all cathepsins will have similar properties to each other or to any other proteases. Cathepsins have been designated by both Roman numerals and by letters. Some of these enzymes have been identified with enzymes purified independently, as cathepsin III with leucine aminopeptidase. Several are activated by sulfhydryl compounds, some by metals. The isolation of the various cathepsins and studies of their substrate specificities are subjects currently under investigation, but because of the lower concentration of enzyme in the source materials and the number of related enzymes present, this area of investigation has not reached the development of the study of digestive enzymes. 

The second step is the proteolytic attack on the peptide chain carried out by a leucine aminopeptidase similar to the kidney enzyme. 

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

In newborn kidney, the reactions of /3-glucuronidase, glucose-6-phos-phatase, and leucine aminopeptidase are positive in the proximal and distal convolutions of the nephrons, but are localized only in the middle and deep regions of the cortex, while the three enzyme reactions are positive in the convoluted tubules of the cortex of the adult kidney. The cortex seems at this stage functionally inactive (Turchini et al., 1965). Some histo-chemical observation on newborn lymphosarcoma has been reported (Shiinada, 1964). 

Although the Edman method is by far the most common method of sequencing peptides from the /V-terminus, some enzymic methods are used occasionally. Several aminopeptidases are available commercially, which differ in their specificities. One aminopeptidase from porcine kidney preferentially releases amino acids such as leucine with hydrophobic side-chains. This enzyme does not release /V-terminal Arg or Lys or any amino acid that is followed by Pro. Another enzyme, aminopeptidase M, which is obtained from the microsomal fraction of porcine kidney cells, is less specific and perhaps more useful. It is advisable to examine aliquots of the hydrolysate at intervals by chromatography to determine the order in which amino acids are being released. 

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