Some enzymes or enzyme complexes require several cofactors. The cells are filled with secretory granules containing the precursor digestive enzymes. Potassium ions are present in a wide variety of proteins and enzymes. Digestion begins in the mouth with the secretion of saliva and its digestive enzymes. Cyproterone acetate can cause elevated liver enzymes and liver damage, including liver failure. Steroids are primarily oxidized by cytochrome P450 oxidase enzymes, such as CYP3A4. It binds with iron in the mitochondrial cytochrome enzymes, thus preventing cellular respiration. Porphyrias are caused by mutations in genes that encode enzymes in heme synthesis. It does this by inhibiting various metabolic enzymes within the bacteria. Microorganisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. Pyruvate dehydrogenase deficiency can result from mutations in any of the enzymes or cofactors. It is a critical component in dozens of proteins and enzymes. These carotenoids are broken down into pigments by liver enzymes. This induces a release of proteolytic enzymes from the vasculature. These adenocarcinomas start within the part of the pancreas which makes digestive enzymes.