Alteration in pH causes inhibition of lysosomal acidic proteases causing a diminished proteolysis effect. The proteasome is also involved in Intracellular antibody-mediated proteolysis of antibody-bound virions. The increased production of cytokines induces proteolysis and breakdown of myofibrillar proteins. Some ribosomal peptides are subject to proteolysis. Lysine 48-linked polyubiquitin chains target proteins for destruction, by a process known as proteolysis. Furthermore, cancer cells tend to produce misfolded proteins, which are removed mainly by proteolysis. This refolding renders the PrP isoform extremely resistant to proteolysis. The C1 complement complex binds to these antibodies resulting in its activation via cross proteolysis. In Alzheimer's disease, APP is divided into smaller fragments by enzymes through proteolysis. Consequently, dis-regulation of proteolysis can cause disease. Currently more than 50 clans are known, each indicating an independent evolutionary origin of proteolysis. TSST-1 is resistant to heat and proteolysis. Proteolysis by protease is required prior to absorption. The arg-gingipain and lys-gingipains are responsible for this proteolysis.