Leucyl-alanine

Leucyl-alanyl-glycine B/< - " ° = P °"y =hloride + alanyl-glycine). Alanyl-leucyl-glycine (a-bromopropionylbromide + leucyl-glycine). Glycyl-leucyl-alanine (chloiacetylchloride + leucyl-alanine). 

The same diketopiperazines are obtainable either from the dipep-tidcs alanyl-leucine or from the dipeptides leucyl-alanine, so that in fact the number of isomers of a diketopiperazine composed of two different amino acids is less than those of the i.somers of the dipeptide composed of the same two amino acids. 

At present only a racemic form prepared from leucyl-alanine by fusion has been obtained its nature has not yet been determined. 

Leucyl-alanine Alanyl-leudne Leucyl-leudne... 

In the earlier experiments by Fischer and Bergell it was found that leucyl-alanine was hydrolysed by an extract of pancreas it was not however hydrolysed by pure pancreatic juice. Such extracts probably contain other enzymes, more especially the autolytic enzyme, which produce the hydrolysis the later work of Abderhalden and his coworkers upon the action of enzymes from various organs also show that polypeptides not hydrolysed by pure tiypsin are attacked by these enzymes (see table, p. 48). 

Therefore, of these three juices the pancreatic juice is without action, the intestinal juice is slightly active, while the yeast juice acts very energetically. Pancreatin reacts vigorously on leucyl-alanin while kinased pancreatic juice is without effect. The behavior with polypeptids indicates, then, a difference between these two products, and the existence in one of an enzyme which is not found in the other. 

Generation of O2 " was inhibited by curcumin, when blood neutrophils from rhesus monkeys were stimulated with arachidonic acid, serum treated zymosan and N-formyl-methionyl-leucyl alanine (Srivastava 1989). 

The pepsin inhibitor itself is split in the presence of pepsin into four different peptides. As crystalline pepsinogen is made of a single peptide chain with a valyl, leucyl, alanine C-terminal polypeptide and leucine N-terminal, the pepsin molecule contains the same C-terminal polypeptide, but its N-terminal is isoleucine instead of leucine. Such a finding suggests that pepsin is the C-terminal moiety of pepsinogen. The determination of the N- and C-terminal amino acids of pepsin is a remarkable achievement in view of the difficulty encountered in obtaining pepsin free of polypeptide. This difficulty stems from the rapid breakdown of the original enzyme. 

Neutrophils represent an ideal system for studying osmotic effects on exocytosis. Stimulation of cytochalasin-B-treated neutrophils with the chemotactic peptide Jlf-formylmethionyl-leucyl-phenyl-alanine (FMLP) results in a rapid compound exocytosis up to 80% of lysosomal enzymes are released within 30 s (9-14). Secretion appears to be triggered by a rise in the level of cytosolic free calcium (15-18) promoted in part by entry of extracellular calcium through receptor-gated channels and in part by release of calcium that is sequestered or bound at some intracellular site (19-21). In this presentation, we augment our previously published data (22,23), which demonstrates that lysosomal enzyme release from neutrophils is inhibited under hyperosmotic conditions and that the rise in cytosolic calcium preceding secretion is inhibited as well. 

N-[N-(benzyloxycarbonyl)-L-aspart-l-oyl-(L-alanyl-L-threonyl-L-leucyl-L-alanine p-nitrobenzyl ester)-4-oyl]-N-[N-(benzyloxycarbonyl)-L-aspart-l-oyl-(L-alanyl-L-threonyl-L-leucyl-L-alanyl-L-serine p-nitrobenzyl ester)-4-oyl]-N-[N-(benzyloxycarbonyl)-L-aspart-1 -oyl-(glycine ethyl ester)-4-oyl -N-[N-(benzyloxycarbonyl)-L-aspart-l-oyl-(glycyl-L-serine methyl ester)-4-oyl]-... 

Phenylalanine reacts with ninhydrin in the presence of a dipeptide (usually glycyl-L-leucine or L-leucyl-L-alanine) to form a fluorescent product. The fluorescence is enhanced and stabilized by the addition of an alkaline copper reagent to adjust the pH to 5.8 and the resulting fluorescence is measured at 515 nm after excitation at 365 nm see Procedure 10.2. 

Figure 2. The structure of DMSO-included Crystal of L-leucyl-L-alanine. (a) A b-c plane. The term L.D. means the layer distance given by PXRD. (b) The sruecture (a-b plane) along with the included DMSO sepresented by CPK model.

L-valyl-L-phenylalanine-2-propanol (1/1) and L-leucyl-L-phenylalanine-2-propanol (1/1) (P-form), Acta Cryst. C55, 2171-2177 d) Gorbitz, C. H. and Torgersen, E. (1999) Symmetry, pseudosymmetry and packing disorder in the alcohol solvates of L-leucyl-L-valine Acta Cryst. B55, 104-113 e) Mitra, S. N., Govindasamy, L. and Subramanian, E. (1996) L-Leucyl-L-alanine dimethyl sulfoxide solvate, Acta Cryst. C52, 2871-2873. 

Inhib. abbrev. DTT = dithioghreitol E64D = epoxysuccinyl-L-leucyl-amido-3-methyl-butane ethyl ester EDTA = ethylene-diamine-tetra-acetic acid EGTA = ethylen-glycol-tetra-acetic acid LHVS = morpholinurea-leucine-homophenyl-alanine-vinylsulfone-phenyl NEM = N-ethyl-maleimide PAI = plasminogen activator inhib. PMSF = phenil-methyl-sulfonil fluoride SBTl = soybean trypsin inhib. TIMP = tissue inhib. of metalloproteinases TPCK = tosyl-L-phenyl-alanyl-chloro-methane Al.so termed stephins. 

Abb. 14. Massenspektrum des N-Acetyl-leucyl-(0-acetyl)threonyl-alanins... 

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). 

Glycyl glutamic acid Glycyl proline Glycyl tryptophan Leucyl glycyl phenylalanine Tryptophanyl alanine Tryptophanyl glycine Tryptophanyl tryptophan Tryptophanyl tyrosine... 

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