Intestinal mucosa leucine aminopeptidase

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... 

One of the earliest suggestions that total enzymatic hydrolysis was possible came from the studies of Frankel (1916), who showed that over 90 % of the bonds in several proteins could be broken when proteolysis with pepsin, trypsin, and chymotrypsin was followed by prolonged hydrolysis with the erepsin preparation of Cohnheim (1901). The recognition in later years of several peptidases in intestinal exti acts which will specifically act upon bonds that are not susceptible to the endopoptidases (Bcrg-mann, 1942) probably accounts for these obseiwations. The specific peptidases such as prolidase, iminodipeptidase (prolinase), glycylglycine dipeptidase, tripeptidase, and leucine aminopeptidase, whi( h are present in mucosa, attack many of the bonds that resist the action of endopoptidases. 

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. 

Disaccharidase, leucine aminopeptidase and glucose uptake in intestinalized gastric mucosa. Gastroenterology, 52 1137. 

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