Pyrimidine synthesis

Question 1

Basic mechanism

Answer 1

a pyrimidine ring is formed from carbomyl phosphate and aspartate from aspartate transcarbamoylase

the thing is then added to a PRPP molecule, and eventually you end up with UTP and CTP to produce TTP and dCTP

Question 2

De Novo synthesis step one

Answer 2

Bicarbonate, glutamine, and ATP are catalyzed by Carbomyl phosphate synthetase II to form

Carbomyl Phosphate

Question 3

De Novo synthesis step two

Answer 3

Committed step

Carbomyl Phosphate is catalyzed with aspartic acid via
Aspartic Transcarbamoylase to form Aspartic Carbomylase

Question 4

De novo synthesis step three

Answer 4

dihydroorotase converts Carbomyl Aspartate to

dihydro orotate , subsequently processed in the mitochondria

Question 5

De novo synthesis step four

Answer 5

dihydro orotate is converted to orotate by
dihydroorotase dehydrogenase

orotate is transfered to cytosol from mito

Question 6

De novo synthesis step five

Answer 6

orotate (now in cytosol) is combined with PRPP to form OMP via UMP synthase

OMP is hydrolyzed to UMP via UMP synthase

deficiency at this stop causes orotic aciduria

Question 7

Orotic acid–> ____ —> _____

Answer 7

orotidylate —> UMP

first step catalyzed by OPRT

Question 8

OPRT

Answer 8

catalyzes orotic acid to orotidylate, which is then converted to UMP