OTC

The OTC gene provides instructions for making the enzyme ornithine transcarbamylase. This enzyme participates in the urea cycle, a series of reactions that occurs in liver cells. The urea cycle processes excess nitrogen, generated when protein is used by the body, into a compound called urea that is excreted by the kidneys. Excreting the excess nitrogen prevents it from accumulating in the form of ammonia, which is toxic, especially to the nervous system.

The specific role of the ornithine transcarbamylase enzyme is to control the reaction in which two compounds, carbamoyl phosphate and ornithine, form a new compound called citrulline.

ornithine transcarbamylase deficiency - caused by mutations in the OTC gene

More than 200 mutations in the OTC gene have been identified. A mutated OTC gene may result in an ornithine transcarbamylase enzyme that is shorter than normal or the wrong shape, or may prevent the enzyme from being produced at all.

The shape of an enzyme affects its ability to control a chemical reaction. If the ornithine transcarbamylase enzyme is misshapen or missing, it cannot fulfill its role in the urea cycle. Excess nitrogen is not converted to urea for excretion, and ammonia accumulates in the body. Ammonia is toxic, especially to the nervous system, so this accumulation causes neurological problems and other signs and symptoms of ornithine transcarbamylase deficiency.