 Antizyme

Antizyme is a regulatory protein that binds ornithine decarboxylase, inhibits its activity and promotes its degradation. This limits a key entry step in polyamine synthesis. Production of antizyme itself can respond to polyamine availability through regulated biological translation, creating feedback between a metabolic product and the lifetime of its biosynthetic enzyme. The inhibitory protein is therefore part of a pathway-control system rather than an additional substrate of the decarboxylase reaction. ^[ref]