amastatin and actinonin

The methionine aminopeptidase (MetAP) catalyzes the removal of amino terminal methionine from newly synthesized polypeptide. MetAP from Mycobacterium smegmatis mc(2) 155 was purified from the culture lysate in four sequential steps to obtain a final purification fold of 22. The purified enzyme exhibited a molecular weight of approximately 37 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Activity staining was performed to detect the methionine aminopeptidase activity on native polyacrylamide gel. The enzyme was characterized biochemically, using L-methionine p-nitroanilide as substrate. The enzyme was found to have a temperature and pH optimum of 50 degrees C and 8.5, respectively, and was found to be stable at 50 degrees C with half-life more than 8 h. The enzyme activity was enhanced by Mg(2+) and Co(2+) and was inhibited by Fe(2+) and Cu(2+). The enzyme activity inhibited by EDTA is restored in presence of Mg(2+) suggesting the possible role of Mg(2+) as metal cofactor of the enzyme in vitro.

Topics: Aminopeptidases; Calcium Chloride; Cobalt; Copper; Electrophoresis, Polyacrylamide Gel; Enzyme Stability; Ferrous Compounds; Hydrogen-Ion Concentration; Hydroxamic Acids; Leucine; Magnesium Chloride; Methionyl Aminopeptidases; Molecular Weight; Mycobacterium smegmatis; Peptides; Temperature

Porphyromonas gingivalis is an asaccharolytic bacterium that requires nitrogen substrates as carbon and energy sources. The aims of this study were to investigate the aminopeptidase activities of P. gingivalis and to evaluate the effect of aminopeptidase inhibitors on bacterial growth. Only arginine aminopeptidase and dipeptidyl aminopeptidase IV activities were detected. Experimental evidence was obtained suggesting that the Arg-gingipains of P. gingivalis can function as both an endopeptidase and an aminopeptidase. Firstly, the arginine aminopeptidase activity was found to be inhibited by leupeptin, a well-known inhibitor of Arg-gingipain activity. Secondly, a preparation of Arg-gingipain activity could hydrolyze the chromogenic substrate for arginine aminopeptidase. Lastly, a mutant of P. gingivalis constructed via gene disruption by use of suicide plasmids and deficient in both Arg-gingipain A and B was also devoid of arginine aminopeptidase activity. To investigate the key role of aminopeptidase activities in growth of P. gingivalis, aminopeptidase inhibitors were incorporated in the culture medium prior to inoculation. Bestatin and actinonin were the only ones to inhibit growth of P. gingivalis. Their mechanism of growth inhibition appears to be different but does not involve inhibition of the two major aminopeptidase activities (arginine aminopeptidase and dipeptidyl aminopeptidase IV).

Topics: Adhesins, Bacterial; Aminopeptidases; Anti-Bacterial Agents; Carbon Radioisotopes; Cathepsins; Chromogenic Compounds; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; Dipeptidyl Peptidase 4; Gingipain Cysteine Endopeptidases; Guanidines; Hemagglutinins; Humans; Hydroxamic Acids; Leucine; Leupeptins; Mutation; Oligopeptides; Peptides; Porphyromonas gingivalis; Protease Inhibitors; Radiopharmaceuticals

The enzymatic changes in murine spleen caused by the administration for 20 successive days of various inhibitors of aminopeptidase N (leucocyte antigen CD13) have been compared. When compared with the control (saline), most of the inhibitors significantly suppressed splenic enzyme activities including those of ectoenzymes. A multivariate study indicated that the in vivo effects of the inhibitors were closely related to their inhibitory actions in vitro.

Topics: Amino Acids; Animals; Anti-Bacterial Agents; CD13 Antigens; Endopeptidases; Glycoside Hydrolases; Guanidines; Hydroxamic Acids; Imidazoles; Leucine; Male; Mice; Mice, Inbred BALB C; Oligopeptides; Peptides; Protease Inhibitors; Spleen

A membrane-bound enkephalin-degrading aminopeptidase was purified from the longitudinal muscle layer of the guinea pig small intestine by four steps of column chromatography using L-tyrosine beta-naphthylamide. The molecular weight of the enzyme was estimated to be 105,000 by gel filtration. The maximum activity was observed between pH 6.5 and 7.0. The Km value for leucine-enkephalin was 137 microM. The aminopeptidase activity toward aminoacyl beta-naphthylamide substrates was restricted to basic, neutral, and aromatic aminoacyl derivatives. No action was detected on acidic amino acid and proline derivatives. The enzyme was potently inhibited by the aminopeptidase inhibitors actinonin, amastatin, and bestatin, and bioactive peptides such as angiotensin III, substance P, and Met-Lys-bradykinin. The enzyme activity was also inhibited by the antibody against the purified serum enkephalin-degrading aminopeptidase of guinea pig at concentrations similar to those at which activity was observed toward serum enkephalin-degrading aminopeptidase and renal aminopeptidase M. The enzyme rapidly hydrolyzed Leu-enkephalin and Met-enkephalin with the sequential removal of the N-terminal amino acid residues. The enzyme also hydrolyzed two enkephalin derivatives, angiotensin III and neurokinin A. However, neurotensin, substance P, and bradykinin were not cleaved. These properties indicated that the membrane-bound enkephalin-degrading aminopeptidase in the longitudinal muscle layer of the small intestine is similar to the serum enkephalin-degrading aminopeptidase and resembles aminopeptidase M. It is therefore suggested to play an important role in the metabolism of some bioactive peptides including enkephalin in peripheral nervous systems in vivo.

Topics: Aminopeptidases; Animals; Anti-Bacterial Agents; CD13 Antigens; Guinea Pigs; Hydrolysis; Hydroxamic Acids; Ileum; Kidney; Leucine; Molecular Weight; Muscles; Neuropeptides; Oligopeptides; Peptides; Substrate Specificity

Actinonin and amastatin are low-molecular-weight inhibitors of aminopeptidases associated with cell surfaces. The purpose of this study was to determine their effects on human neutrophil functions such as chemotaxis and phagocytosis. Both actinonin and amastatin enhanced chemotaxis to the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine. On the other hand, the effects of both agents on neutrophil phagocytosis were varied. Bacterial attachment to neutrophils was slightly affected by these agents. However, actinonin enhanced the internalization of bacteria by neutrophils. Neutrophil leucine aminopeptidase activity was also determined and was found to be weakly inhibited by these agents.

Topics: Anti-Bacterial Agents; Chemotaxis; Humans; Hydroxamic Acids; In Vitro Techniques; Neutrophils; Oligopeptides; Peptides; Phagocytosis; Regression Analysis