Top Posters
Since Sunday
5
o
5
4
m
4
b
4
x
4
a
4
l
4
t
4
S
4
m
3
s
3
SlideshowReport

The de novo pathway for purine synthesis.

Description
The first purine product of this pathway, IMP (inosinic acid or inosine monophosphate), serves as a precursor to AMP and GMP. Step 1: PRPP synthesis from ribose-5-phosphate and ATP by ribose-5-phosphate pyrophosphokinase. Step 2: 5-Phosphoribosyl-b-1-amine synthesis from a-PRPP, glutamine, and H2O by glutamine phosphoribosyl pyrophosphate amidotransferase. Step 3: Glycinamide ribonucleotide (GAR) synthesis from glycine, ATP, and 5-phosphoribosyl-b-amine by glycinamide ribonucleotide synthetase. Step 4: Formylglycinamide ribonucleotide synthesis from N10-formyl-THF and GAR by GAR transformylase. Step 5: Formylglycinamidine ribonucleotide (FGAM) synthesis from FGAR, ATP, glutamine, and H2O by FGAM synthetase (FGAR amidotransferase). The other products are ADP, Pi, and glutamate. Step 6: 5-Aminoimidazole ribonucleotide (AIR) synthesis is achieved via the ATP-dependent closure of the imidazole ring, as catalyzed by FGAM cyclase (AIR synthetase). (Note that the ring closure changes the numbering system.) Step 7: Carboxyaminoimidazole ribonucleotide (CAIR) synthesis from CO2, ATP, and AIR by AIR carboxylase. Step 8: N-succinylo-5-aminoimidazole-4-carboxamide ribonucleotide (SAICAR) synthesis from aspartate, CAIR, and ATP by SAICAR synthetase. Step 9: 5-Aminoimidazole carboxamide ribonucleotide (AICAR) formation by the nonhydrolytic removal of fumarate from SAICAR. The enzyme is adenylosuccinase. Step 10: 5-Formylaminoimidazole carboxamide ribonucleotide (FAICAR) formation from AICAR and N10-formyl-THF by AICAR transformylase. Step 11: Dehydration/ring closure yields the authentic purine ribonucleotide IMP. The enzyme is IMP synthase.
Related Images
Add Comment
Explore
Post your homework questions and get free online help from our incredible volunteers
  844 People Browsing
 112 Signed Up Today
Your Opinion
Which country would you like to visit for its food?
Votes: 204

Previous poll results: How often do you eat-out per week?