The CPS1 gene encodes carbamoyl phosphate synthetase I, a mitochondrial enzyme that catalyzes the first and rate-limiting step of the urea cycle by synthesizing carbamoyl phosphate from ammonia and bicarbonate. [5] [6] This crucial reaction enables the safe removal of excess nitrogen from the body by converting toxic ammonia into urea, which is then excreted by the kidneys. [6] Mutations in the CPS1 gene can lead to carbamoyl phosphate synthetase I deficiency, an inherited metabolic disorder that causes hyperammonemia and can have severe neurological consequences if untreated. [7]