1. Proteolytic enzyme activities in rat peritoneal exudate
M Pásztor, J Fischer, Z Nagy, I Sohár Acta Biol Hung. 1991;42(1-3):285-95.
Proteinase activities in rat thioglycollate elicited peritoneal cells and the cell-free supernatant (lavage fluid) were measured by using the following substrates: Suc-Ala-Ala-Pro-Phe-Methyl-Coumarin-Amide (for cathepsin G or chymase), Suc-Ala-Ala-Ala-AMC (for elastase or elastase-like), Z-Arg-Arg-AMC (for cathepsin B), haemoglobin (for cathepsin D) and Ala-AMC (for alanine-aminopeptidase: AAP). The enzyme activities were correlated to the quantitative distribution of various cell types in the exudate from 0 to 192 nd h. In the supernatant all the examined activities showed a higher value at 72nd h. In the cells activity of chymase and AAP proved to be very high at 0 h but after four h the activities were dropped. From this time all enzyme activities started to elevate till the 24th h. At the 96th h only the activity of cathepsin B and AAP had a high value. We conclude that the intracellular activation and secretion of proteolytic enzymes characteristic for the various peritoneal cell types involved in the acute and chronic inflammatory reaction can be followed by activity measurements using enzyme-specific substrates and inhibitors.
2. A zinc metalloendopeptidase associated with dog pancreatic membranes
R A Mumford, A W Strauss, J C Powers, P A Pierzchala, N Nishino, M Zimmerman J Biol Chem. 1980 Mar 25;255(6):2227-30.
Assay of solubilized dog pancreas microsomes revealed the presence of an endopeptidase which hydrolyzed the fluorogenic peptide substrate Suc-Ala-Ala-Phe-7-amino-4-methylcoumarin (AMC) between the alanine and phenylalanine positions. This activity was inhibited by phosphoramidon, 1,10-phenanthroline, and a number of synthetic inhibitors of thermolysin indicating that the enzyme is a zinc metallopeptidase. Endopeptidase activity was not inhibited by the serine protease inhibitors elastatinal, antipain, leupeptin, N-carbobenzyloxy-L-phenylethyl chloromethyl ketone, L-tosylamido-2-lysyethyl chloromethyl ketone, L-tosylamido-2-phenylethyl chloromethyl ketone, phenyl-methanesulfonyl fluoride, or low levels of chymostatin. The endopeptidase had a pH optimum between 7.0 and 7.5. The enzyme also hydrolyzed Suc-Ala-Ala-Ala-AMC and Suc-Ala-Gly-Ala-AMC in an analogous way to yield Ala-AMC. Thermolysis hydrolyzed Suc-Ala-Ala-Phe-AMC in an analogous way to the endopeptidase. However, thermolysin did not hydrolyze Suc-Ala-Ala-Ala-AMC or Suc-Ala-Gly-Ala-AMC, demonstrating that its substrate specificity differs from the endopeptidase.
3. Cold-induced apoptosis of rat liver endothelial cells: involvement of the proteasome
Thorsten R Doeppner, Tilman Grune, Herbert de Groot, Ursula Rauen Transplantation. 2003 Jun 27;75(12):1946-53. doi: 10.1097/01.TP.0000065291.02855.6A.
Background: We have previously shown that in cultured liver endothelial cells the mere sequence of hypothermia and rewarming induces a pronounced, iron-dependent apoptosis that is likely to contribute to hepatic preservation injury. Here we study the involvement of proteases in this cold-induced apoptosis. Methods: Cultured liver endothelial cells were incubated in preservation solutions at 4 degrees C in the absence or presence of protease inhibitors. Cell injury and different protease activities were assessed. Results: Cold incubation of liver endothelial cells in University of Wisconsin or histidine-tryptophan-ketoglutarate (HTK) solution led to marked cell injury, which was strongly inhibited by the protease inhibitor 3,4-dichloroisocoumarin (DCI) (lactate dehydrogenase release: 86.0+/-2.6% in HTK and 4.0+/-0.4% in HTK + DCI after 24 hr of cold incubation). Determination of protease activity showed a doubling in the activity of a Suc-Leu-Leu-Val-Tyr-AMC-cleaving protease and some increase in a relatively low Suc-Ala-Ala-Ala-AMC-cleaving activity after 8 hr of cold incubation in HTK solution or 16 hr in University of Wisconsin solution. Further characterization of the protease activities showed that they belonged to two different proteases, with the major activity being calcium independent, inhibited by DCI, MG-132, and lactacystin, and strongly decreased by immunoprecipitation with an antiproteasome antibody. Preincubation of the cells with the iron chelator deferoxamine prevented the cold-induced increase of both activities. Conclusion: These results show that (i) the proteasome and possibly, in addition, a serine protease are involved in cold-induced apoptosis of liver endothelial cells and (ii) the protease activation is downstream from the increase in intracellular chelatable iron.
