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Medical Definition of Carbamoyl phosphate synthetase
1. A phosphotransferase catalyzing the formation of carbamoyl phosphate. There are two significant isozymes. Carbomoyl phosphate synthetase I is a mitochondrial enzyme that catalyses the reaction of 2ATP, NH3, CO2, and H2O to carbamoyl phosphate, 2ADP, and Pi. It is activated by N-acetylglutamate and participates in urea biosynthesis. A deficiency of carbamoyl phosphate synthetase I can result in hyperammonaemia. Carbamoyl phosphate synthetase II is a cytosolic enzyme that, under physiological conditions, uses l-glutamine as the nitrogen source (producing l-glutamate) instead of NH3, is not activated by N-acetylglutamate, and is found in pyrimidine biosynthesis. (05 Mar 2000)