The protein ornithine decarboxylase (ODC) functions to decarboxylate ornithine into putrescine. This is important because it is the first and rate-limiting step in the formation of polyamines. Polyamines bind to DNA, RNA, and negative proteins, and are important for cell growth and proliferation. The natural substrate of ODC is ornithine (a product of the urea cycle) and the enzyme needs cofactor pyridoxal 5’phosphate (PLP) to function. In this model ODC is inhibited by the drug G418 (geneticin), which is used to treat African sleeping sickness and is a potential drug to treat cancer/cell proliferative diseases. Some annotations show the active site where ornithine binds and how it is separate to the binding site of the drug. Other annotations will show how the drug causes allosteric inhibition by changing residues in the active site and disordering a 10-residue interface loop.
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