CH 22: Catabolism of Nucleic Acids and Nucleotides. Anabolism of Nucleotides Flashcards
Catabolism of nucleic acid
How are nucleic acids degraded to nucleotides?
Nucleases
Catabolism of nucleic acid
What are the two types of nucleases?
Endonuclease: cuts DNA/RNA at a specific site inside
Exonuclease: cuts 1 nucleotide at a time from either the 5’ or 3’ end
Catabolism of nucleic acid
Why are nucleotides important?
- Precursor for DNA/RNA synthesis
- essential carriers of chemical energy (like ATP)
- components of NAD+, FAD, and coenzyme A
- Form activated intermediates (UDP-glucose and CDP-diacylglycerol)
- cAMP and cGMP are cellular second messengers
Catabolism of nucleotide
What is the order and enzymes for nucleotide catabilism?
Nucleotide (using nucleotidase)
* Nucleoside (using Nucleosidase)
* Bases
* Purine
* Pyrimidine
* Ribose/deoxyribose
* Phosphate
Purine Cataolism
What does purine degrade into?
Uric Acid
Purine Cataolism
What is the point of convergence for the metabolism of purine bases?
Xanthine
Purine Cataolism
What enzyme converts Xanthine to uric acid?
Xanthine oxidase
Purine Cataolism
What is the inhibitor for xanthine oxidase?
Allopurinol
Purine Cataolism
What happens if there is excess uric acid being made without inhibition?
It will build up them precipitate into joints, causing Gout
Purine Cataolism
How is AMP made into Uric Acid?
Removal of amino group first then removal of sugar
Purine Cataolism
How is AMP made into Uric Acid?
Removal of sugar first then the removal of the amino group
Purine Cataolism
Why is Inosine still a nucleoside?
The sugar hasn’t been removed yet, only the amino group.
Pyrimidine Cataolism
What does Pyrimidine degrade into?
CO2, NH3, and B-AA
Pyrimidine Cataolism
What AA do C/U degrade to?
B-alanine
Pyrimidine Cataolism
What AA does T degrade to?
B-aminoisobutirate
Pyrimidine Cataolism
What does dehydrogenase do?
it adds hydrogen to the molecules
Pyrimidine Cataolism
What does hydrolase do?
breaks the ring then splits the pyrimidine into pieces
Anabolism of nucleotides
What are the two pathways that lead to nucleotides?
De novo pathway: Assembly of a compound from simpler molecules not salvaged from pre-existing similar molecules. It begins with their metabolic precursors: AAs, ribose-5-phosphate, CO2
salvage pathway: synthesis of nucleotides by recyling the free bases and nucleosides from nucleic acid breakdown
Anabolism of nucleotides
What are the benefits of the salvage pathway?
Saves fuel and energy
Some tissues/organs (brain and bone marrow) can only use the salvage pathway.
De novo biosynthesis of purines
Where does De novo synthesis begin?
with a reaction of 5-phosphoribosyl 1-pryophosphate (PRPP) with Gln
De novo biosynthesis of purines
What is the first intermediate formed with a full purine ring? What get formed from this intermediate?
inosinate (IMP)
AMP and GMP
Purine Salvage Pathway
What type of enzyme is used to salvage the pieces into AMP/IMP/GMP?
phosphoribosyl transferase (adenine for AMP, hypoxanthine-guanine for IMP/GMP)
IMP’s base is hypoxanthine
De novo biosynthesis of pyrimidines
What are pyrimidines formed using?
Asp, PRPP, and carbamoyl phosphate
De novo biosynthesis of pyrimidines
How does pyrimidine synthesis start?
FIrst by making the pyrimidine ring then attaching it to the ribose-5-phosphate
