Ornithine decarboxylase (ODC) is a homodimer of 461 amino acids (in humans, at least) that catalyzes the decarboxylation of ornithine producing, as a result, diamine putrescine?. This is the first step and the rate limiting step in humans for the production of polyamines?, compounds required for cell division.
The Ornithine Cycle. The amino acid ornithene is 'non-essential' in the sense that it can be made from other amino acids, such as arginine or citrulline. Polyamine synthesis begins with the conversion of ornithene into the polyamine putrescine by the action of the enzyme ornithene de-carboxlase (ODC)
ODC the first enzyme in the biosynthesis of polyamines in all mammal cell. It is also called the 'rate limiting' enzyme, because it lies at a choke point by which you can control the production of other polyamines by controlling ODC.
The control over ODC (and consequently over polyamines) is very exquisite and precise. Cell growth and differentiation are dependent on precise control of the levels of polyamines inside the cell. ODC is one of those ephemeral enzymes that don't last very long in the cell: protein-splitting enzymes degrade it very rapidly. This is known as a 'half-life,' which is just the amount of time for the original amount of a chemical in the body to drop by half. The half-life of ODC is one of the shortest known for any enzyme in any species of mammal, and which gives the cell a way to rapidly change polyamine synthesis.
Inhibition of ODC results in a drop in polyamine synthesis and an arrest of cell growth; sometimes this can be reversed by the use of external polyamines from the diet. Not surprisingly, human cells are equipped with a very efficient transport system for snaring these extracellular polyamines and putting them to work.
Foods than inhibit ODC
- Curcumin (found in tumeric)
- Green tea
- Broccoli leaves
- Black currant fruit