Increased excretion of N-carbamoyl compounds in patients with urea cycle defects.

Increased urinary levels of N-carbamoyl-beta-alanine, and also, on occasions, of N-carbamoylaspartate, were observed in patients with ornithine carbamoyl-transferase (EC 2.1.3.3) deficiency, argininosuccinate synthetase (EC 6.3.4.5) deficiency and argininosuccinate lyase (EC 4.3.2.1)deficiency, but not in a patient with carbamoylphosphate synthase deficiency. The relevance of these findings to the diagnosis of urea cycle defects is discussed.