Some unusual manifestations of proteolysis

In the article the results of the long-term researches revealing the essence of the following three phenomena are generalized. 1. Participation of active oxygen species (especially, superoxide radical) in activation of zymogens--plasminogen, trypsinogen, chymotrypsinogen, pepsinogen and in realization of the catalytic (proteolytic) function of a number of proteinases. The essence of the hypothesis of oxygen-dependent reactions of proteolysis is stated. As shown by the example of mouse brain homogenate fractions, the plasminogen-activating ability of the fractions can also be realized via this way. From the positions of these views the experimental facts obtained about the influence of streptokinase and plasminogen on vital activity of nervous tissue cells are analysed. 2. Suppression of proteolytic reactions by ATP: plasminogen-activating ability of streptokinase, gamma- and betasubunits of the nerve growth factor, proteolytic activity of Arthrobothrys longa proteinases, destroyed cells of Corynebacterium diphtheriae PW-8. In some cases a significant effect was reached at concentration of ATP < or = 0.001 M. The effect depends on protein substrates used. 3. The increase of fibrinolytic activity of the mitochondrial fraction of the mouse brain and liver, proteolytic activity of human lymphoblasts of transplanted lines in the presence of inorganic orthophosphate. Judging by the results of inhibitory analysis, it is not caused by the resynthesis of ATP in the system and has an independent character--"phosphate effect" in proteolysis. 4. The results of our researches of formation of stable equimolar complexes of streptokinase or plasminogen with enzymes of carbohydrate-energetic metabolism are briefly analysed. The results of researches of functional properties of the molecules of diphtheria toxin, the nerve growth factor and it subunits are summarized. A number of fundamental and applied consequences of these phenomena are considered.