Fig. 4. Pathway for citrulline and arginine synthesis from glutamate. The names of enzymes functioning in the metabolic steps from 1 to 12 are as follows: 1, N‐acetylglutamate synthase; 2, N‐acetylglutamate kinase; 3, N‐acetylglutamate phosphate reductase; 4, N‐acetylornithine aminotransferase; 5, N‐acetylornithine deacetylase (DRIP‐1 may function for this step); 6, glutamate N‐acetyltransferase; 7, ornithine transcarbamylase; 8, arginosuccinate synthase; 9, arginine synthase; 10, arginase; 11, glutaminase and glutamate dehydrogenase; and 12, carbamoyl phosphate synthetase.