Carbamyl phosphate synthetase deficiency

Carbamyl phosphate synthetase (CPS) (EC 6.3.4.16) (Figure 30.1) is a mitochondrial enzyme catalyzing the formation of carbamylphosphate from ammonia in what is generally considered to be the first step in the urea cycle. Its deficiency is quite rare, compared with ornithine transcarbamylase deficiency, and usually presents with potentially lethal neonatal hyperammonia [1]. There are even rarer mutations, which lead to partial residual activity and a later onset, even adultonset pattern of disease [2].