Purine Metabolism

Front 1

What are functions that Nucleotides are involved in?

Back 1

Replication, Transcription, Energy Metabolism (ATP and GTP), Physiological Mediators (cAMP, cGMP. etc.) Components of coenzymes, Allosteric Modulators

Front 2

True or False? The total amount of AMP+ADP +ATP is always constant, but there are variations of each individual component.

Back 2

True, salvage and de novo pathways keep shiz constant.

Front 3

What are the 3 components of Purine Synthesis?

Back 3

Amino Acids, Tetrahydrofolate, Carbon dioxide

Front 4

Where does De novo purine synthesis take place at?

Back 4

Cytosol in most cells, but RBCs

Front 5

What is Inosine monophosphate?

Back 5

IMP is a common mediator of synthesis of both AMP and GMP. Formation to IMP is a branched pathway.

Front 6

How many ATP to create an IMP?

Back 6

6

Front 7

What is a common reactant in all de novo and salvage pathways?

Back 7

PRPP.

Front 8

What is a precursor to PRPP?

Back 8

5-phsphoribose. It reacts with ATP and PRPP synthetase. This step is not part of the de novo pathway. It's used in all pathways. Highly regulated step which requires high levels of inorganic phosphate and is inhibited by other nucleotides.

Front 9

How is PRA synthesized?

Back 9

PRPP reacts with glutamine PRPP amidotransferase to transfer a nitrogen from the amide group on teh amindo acid glutamine to the PRPP.

Front 10

What is the commited step of de novo synthesis of Purines?

Back 10

PRA syntheses. once this happens, IMP must be formed. It is also the rate-limiting step. and is higly regulated. There is no regulation of IMP synthesis after this step.

Front 11

What are some regulators of PRA synthesis?

Back 11

AMP, IMP, or GMP will negatively inhibit PRA synthesis, Whereas formation of PRPP will positively regulate it's formation.

Front 12

Where do all the pieces of IMP come from?

Back 12

See chart

Front 13

What is IMP a precursor for?

Back 13

AMP and GMP of course

Front 14

What does synthesis of AMP require as an energy source?

Back 14

GTP

Front 15

What doe Synthesis of GMP require as an energy source?

Back 15

ATP

Front 16

Where does the Nitrogen come from on GMP?

Back 16

Glutamine being added to XMP

Front 17

Where does the Nigrogen come from on AMP?

Back 17

Aspartate being added to the Adenylosuccinate.

Front 18

Purine NTP's are formed from either AMP or GMP by the actions of which two enzymes?

Back 18

Nucleoside monophosphate kinases or Nucleotide 5'-diphosphate kinases. This stage of synthesis is unregulated

Front 19

What is Purine salvage biosynthesis?

Back 19

It is when stray purine nucleobases can be resused to give nucleotides. It is much more energetically favorable than de novo purine synthesis. THe salvage pathways and the de novo pathways are innterconnected.

Front 20

Which two enzymes are responsible for Purine Salvage Biosynthesis?

Back 20

HGPRT and APRT both catalzye the reaction of Guanine and Adenine I(the nucleobases with PRPP to give the nucleotide.

Front 21

What inhibits HGPRT?

Back 21

IMP and GMP.

Front 22

What inhibits APRT?

Back 22

AMP

Front 23

What does the purine salvage pathway inhibit?

Back 23

De novo synthesis. It lowers the level of PRPP and raises the level of purine NTP. Both these inhibit de novo synthesis.

Front 24

How are purine nucleosides salvaged? With which enzyme/

Back 24

5' phosphotransferases. One example is adenosine kinase which phosphorylates teh 5; position of adenosine to give AMP. Each nucleoside has its own specific kinase.

Front 25

What inhibits AmP conversion to IMP?

Back 25

GTP and GDP. It is enhanced by ATP.

Front 26

What is inhibits GMP conversion to IMP?

Back 26

XMP. It is enhanced by GTP

Front 27

What do purines catabolize into?

Back 27

Uric acid.

Front 28

Is purine catabolism regulated?

Back 28

Not at all?

Front 29

What do nucleases do?

Back 29

nucleic acids. (DNA or RNA. Once a nucleotide is freed then specific enzymes continue breakdown.

Front 30

GMP will go be dephosphoralated to?

Back 30

Guanosine

Front 31

Guanosine will be deri osylated to give

Back 31

Guanine

Front 32

Guanine is deaminated to give?

Back 32

Xanthine

Front 33

What are the 2 pathways of Adenine Catabolism?

Back 33

Deaminated and then dephosphorylated or
Dephosphorylated and then deaminated. Both pathways go to Inosine. Then inosine will get deribosylated to hypoxanthine and oxidized to give xanthine.

Front 34

What is xanthine oxidized to?

Back 34

Uric acid.

Front 35

What is Allopurinol?

Back 35

Xanthine Oxidase inhibitor and prevents formation of Uric Acid.

Front 36

What disease is X-linked, and shows deficiency of HGPRT?

Back 36

Lesch-Nyhan Syndrome