Ornithine transcarbamoylase(EC 2.1.3.3) is an enzyme of the urea cycle in the liver, that adds carbamoyl phosphate to ornithine forming citrulline.

This enzyme is necessary to put get the ammonia that's incorporated into carbamoyl phosphate, into the urea cycle to get rid of it as urea.

Ornithine transcarbamoylase deficiency

If a person is deficient in this enzyme, ammonia levels will build up, and this will cause neurological problems. Levels of the amino acids glutamate and alanine, will be increased (as these are the amino acids that receive nitrogen from others).

Levels of urea cycle intermediates may be decreased, as carbamoyl phosphate cannot replenish the cycle. The carbamoyl phosphate instead goes into the uridine monophosphate synthetic pathway. Here orotic acid (one step of this alternative pathway) levels in the blood are increased.

A potential treatment for the high ammonia levels is to give sodium benzoate, which combines with glycine to produce hippurate, at the same time removing an ammonium group.