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34 Cards in this Set

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Name this shit!
For purine synthesis, what do we need to start out with?
PRPP (5-phosphoribosyl 1 pyrophosphate)
How do you make PRPP?
From Ribose 5 phosphate of the Pentose phosphate pathway and use the enzyme PRPP synthetase.
What is the first committed step of purine synthesis?
PRPP becomes 5-phosphoribosylamine with the help of glutamine-PRPP amidotransferase.
In purine synthesis, what is the first purine made?
From Inosinate (IMP), what is used for AMP synthesis?
From Inosinate (IMP), what is used for GMP synthesis?
IMP is the precursor for what? x 2
If ATP is higher than GTP, more IMP will be converted to what?
If GTP is higher than ATP, more IMP will be converted to what?
Reciprocal use of GTP and ATP does what?
Equilibrates AMP and GMP synthesis
What regulates PRPP and how?
AMP, GMP, and IMP in an inhibitory manner
What regulates Glutamine PRPP amidotransferase and how?
AMP, GMP, and IMP in an inhibitory manner
What regulates adenylosuccinate synthetase?
AMP in an inhibitory manner
What regulates IMP dehydrogenase?
GMP in an inhibitory manner
Answer this!
In pyrmidine synthesis, what do you need to start out wtih and how do you make it (enzyme and reactant)
You need Carbamoyl phophate made from glutamine and carbamoyl synthetase II.
Where is carbamoyl phosphate made?
Carbomoyl synthetase I - where is it, what does it do, and act in what cycle?
In mitochondria and utilizes NH4 as a nitrogen source.

Also seen in Urea cycle
What is the first committed step of pyrimidine synthesis?
Carbamoyl Phosphate + Aspartate ---> N-Carbamoylaspartate

Use of Aspartate transcarbamolyase
What is CAD?
A multifunctional trimer enzyme that is:
1. Carbamoyl Synthetase II
2. Aspartate transcarbamoylase.
3. Dihydroorotase
What does dihydrooratase catalyze?
N-carbamoylaspartate to dihydroorotate. (RING CLOSURE)
What happens to dihydroorotate?
Diffuses to mitochondria where it is oxidized by dihydroorotate dehydrogenase in to orotate.
What happens to orotate?
Orotate and PRPP (with the enzyme Orotate phophoribosyl transferase) is converted into Orotidylate.
What happens to orotidylate?
Orotidylate with the help of orotidylate decarboxylase becomes UMP (uridylate)
What happens to UMP?
Kinase acts on it to become UTP
Describe the character of orotate phosphoribosyl transferase AND orotidylate decarboxylase.
They are on the same damn enzyme.
What happens to UTP?
UTP becomes CTP with the help of Cytidylate synthetase, glutamine, and ATP
How is Carbamoyl Synthetase II regulated?
ATP and PRPP activate it
UTP and CTP inhibit it
What does UMP regulate?
Inhibits OMP
A rare example occurs where the first commited step is not the regulated step. Why?
Because carbamoyl phosphate is made in the Urea cycle.
What is oroticaciduria type I?
A defect in the orotate phosphoribosyltransferase AND orotidyl decarboxylase.
What is oroticaciduria type II?
A defect in the orotidyl decarboxylase
What are the symptoms of patients with oroticaciduria?
Anemia, and high levels of orotate accumulation.