amastatin and leupeptin

Both thrombin and tryptase have been shown to induce smooth muscle cell proliferation in vitro. We have used cultured primary guinea-pig tracheal smooth muscle in order to define pharmacologically the receptors involved in this effect. Tryptase, a protease-activated receptor (PAR)-2 agonist, induced DNA synthesis up to the second passage of the cells, thereafter the response waned. In contrast, thrombin, a PAR-1 agonist, and the PAR-1 activating peptide (SFLLRN) induced DNA synthesis starting from the third passage only. Thrombin and tryptase responses were dose-dependently inhibited by leupeptin. The selective PAR-2 activating peptide (SLIGRL-NH(2)) was unable to induce DNA synthesis in cells from passages 1 to 6. In agreement with the functional data, mRNA expression for PAR-1 was increased in cells in later passages. In contradiction with the functional data, however, equal mRNA expression for PAR-2 was found in all passages. These results suggest that thrombin induces guinea-pig tracheal smooth muscle DNA synthesis through activation of PAR-1. However, the differential effect of tryptase and SLIGRL-NH(2) suggests that tryptase might exert some of its effect via a non-PAR-2 receptor.

Topics: Actins; Animals; Cell Division; Cells, Cultured; DNA; Guinea Pigs; Humans; Leupeptins; Muscle, Smooth; Peptides; Protease Inhibitors; Receptor, PAR-1; Receptor, PAR-2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Serine Endopeptidases; Thrombin; Thymidine; Trachea; Tryptases

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

An antitumor antibiotic C-1027, a complex protein consisting of an apoprotein and a non-covalently bound chromophore, showed some aminopeptidase activity, 1/15 (on the basis of activity per mg protein) that of porcine kidney enzyme [E.C. 3.4.11.2] by use of L-phenylalanyl 4-methyl-coumaryl-7-amide as the substrate. Neither the apoprotein alone nor the chromophore alone were active. Amastatin and bestatin but not leupeptin inhibited the activity. The enzyme activity of the holo-antibiotic, as opposed to that of the porcine kidney enzyme, was readily lost by UV irradiation, indicating that the intact structure of the chromophore was needed to maintain the native conformation of the holo-antibiotic. The cytotoxicity of the holo-antibiotic, but not that of the chromophore, to Ehrlich carcinoma cells in vitro was reduced to 1/5 by 1 microgram/ml of amastatin which alone had no effect on cell growth. The porcine aminopeptidase was not cytotoxic at all even at higher concentrations (higher enzyme activities/ml). Amastatin possibly occupied the catalytic domain of the holo-antibiotic, interfering with the binding of the holo-antibiotic with some cell-surface protein(s). Amastatin did not inhibit the holo-antibiotic to cleave isolated DNA.

Topics: Aminoglycosides; Aminopeptidases; Animals; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Apoproteins; Carcinoma, Ehrlich Tumor; Cell Survival; DNA, Neoplasm; Enediynes; Leucine; Leupeptins; Microsomes; Oligopeptides; Peptides; Proteins; Substrate Specificity; Swine; Tumor Cells, Cultured; Ultraviolet Rays