title: [Threshold mechanism of the control of cascade proteolysis].
abstract: The immune lysis rate of erythrocytes vs. the concentration of particular complement components was studied. It was found that in the presence of component C1 (but not C3) and factors B and D, the cells undergo lysis after the concentration of these compounds exceeds a "threshold" value. The threshold molar concentrations of factors D and B exceeded 5- and 20-fold, respectively, that of component C1. The multiplicity and different capacities of the thresholds allow the fragmentary activation of cascade proteolysis at stretches between neighboring thresholds without the total realization of the final effect of the system (cell lysis, clot formation, etc.). The resulting peptideby-products (bypass peptides) may possess their own biological activity. It is the generation of various bioregulators that appears to be the main function of the cascade proteolytic systems functioning in the subthreshold regime.
authors.affiliation: Pavlov State Medical University, St. Petersburg, Department of Biochemistry, Russia. igshc@spmu.rssi.ru
authors.forename: I G
authors.initials: IG
authors.lastname: Shcherbak
mesh_terms: D000818:Animals; D003167:Complement Activation; D003172:Complement C1 / Q000276:immunology / Q000378:metabolism*; D003176:Complement C3 / Q000276:immunology / Q000378:metabolism; D015941:Complement Hemolytic Activity Assay; D003170:Complement Pathway, Alternative / Q000276:immunology / Q000502:physiology; D006461:Hemolysis / Q000276:immunology / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D012756:Sheep
chemical_list: D003172:Complement C1; D003176:Complement C3
vernacular_title: Porogovyĭ mekhanizm kontrolia kaskadnogo proteoliza.