Final answer:
The cytosolic enzyme for pyrimidine synthesis that requires ATP is carbamoyl phosphate synthetase II, analogous to carbamoyl phosphate synthetase I in the urea cycle.
Step-by-step explanation:
Cytosolic Enzyme and Urea Cycle
The enzyme in question is carbamoyl phosphate synthetase II (CPS II), which is involved in the cytosolic synthesis of pyrimidines. This enzyme catalyzes an ATP-requiring step and is analogous to carbamoyl phosphate synthetase I (CPS I) in the mitochondria, which participates in the urea cycle. Both enzymes are essential for their respective pathways: CPS II for nucleotide synthesis and CPS I for detoxifying ammonia through the urea cycle.
The urea cycle involves five intermediate steps, each catalyzed by a different enzyme, to convert ammonia to urea. The details from the provided information confirm that the first two steps of the urea cycle occur in the mitochondria and the remaining three are completed in the cytosol. This includes the formation of carbamoyl phosphate by CPS I in the mitochondria, which is the first committed step of the urea cycle requiring ATP and N-acetyl glutamate for activation.