Question

Calculate the the number of ATP consumed (or produced) to synthesize CTP from the following ingredients:
Asp, 2 NH₃, CO₂, Ribose-5-phosphate

Answer 1

Answer- 6ATP are consumed and NADH+H+ produced

1. In first reaction catalyzed by carbamoyl phosphate synthetase, 2ATP are utilized and carbamoyl phosphate is synthesized from CO2 and NH3. Then L-dihydroorotate is converted into orotate by enzyme dihydroorotate dehydrogenase and NAD+ is reduced to NADH+H +.

2.when orotate is converted into orotidylate by orotate phosphoribosyl transferase, 5-phosphoribosyl -1- pyrophosphate is used (PRPP) and during synthesis of PRPP from ribose 5- phosphate 1ATP is utilized by enzyme PRPP synthetase.

3. When uridylate is converted into UTP by the enzyme kinase, 2ATP are utilized and converted into 2ADP.

4. In last step, when UTP is converted into CTP by the enzyme cytidylate synthetase 1ATP is utilized and converted into ADP and Pi.

so that totally for synthesis of CTP from Asp, NH3, CO2 and ribose 5- phosphate 6ATP are consumed.