Rheumatology 3 - Crystal Arthropathies Flashcards
Purines in DNA and RNA
Adenine (adenosine) and Guanine (guanosine)
Pyrimidines in DNA
Thymine (thymidine) and Cytosine (cytidine)
Pyrimidines in RNA
Uracil (uridine) and Cytosine (cytidine)
Sugar + Base
Nucleoside
Nucleoside + 1-3 phosphates
Nucleotide
Purine nucleotide biosynthesis pathways
- De novo pathway
- Salvage pathway
In purine de novo synthesis, what is used to transfer N to PRPP? What is the result?
Glutamine; phosphoribose with an added N
What atoms/molecules supply the C, H, O and N to make a nucleotide?
Other amino acids, CO2, folate (B9)
What is the nucleotide product of purine de novo synthesis?
inosine monophosphate (IMP)
IMP can be used to make ____ or _____
AMP or GMP; these pathways can also use GTP to make AMP, and ATP to make GMP
Why is reciprocal control in the de novo pathway of purines useful?
Helps ensure you are not making all of one type of purine and not enough of the other
Purine salvage pathway uses what molecules that already exist?
Hypoxanthine, guanine, and adenine bases
Where do the existing bases come from?
Diet or normal cell turnover
Enzyme that catalyzes addition of sugar+P to hypoxanthine or guanine? Products?
Hypoxanthine-guanine phosphoribosyl transferase
Hypoxanthine => IMP
Guanine => GMP
Enzyme that catalyzes addition of sugar+P to adenine? Product?
Adenine phosphoribosyl transferase
Adenine => AMP
De novo synthesis of Pyrimidines involves making what first? Then what?
Makes an intermediate pyrimidine ring first, then attaching the ribose-5-P
Substrates for pyrimidine ring are?
Carbamoyl phosphate and Aspartate
How to make CTP?
UMP phosphorylates => UTP
UTP aminated (glutamine) => CTP
How to make dTMP?
UMP phosphorylated => UDP
UDP converted => dUMP
dUMP methylated using B9 => dTMP
What does the “d” mean in dTMP?
deoxy- form (one less oxygen)
Enzyme that removes phosphates from nucleotides => nucleosides?
Nucleotidases
What are pyrimidine bases degraded to?
Cytosine and uracil then ultimately alanine
What are purine bases degraded to?
Xanthine and then uric acid, which is excreted in urine
Enzyme used to convert hypoxanthine to xanthine and xanthine to uric acid?
Xanthine Oxidase
What is gout commonly caused by? Less commonly caused by?
Commonly underexcretion of uric acid
Less commonly overproduction of uric acid
Deposition of monosodium urate crystals in the joints that triggers an inflammatory immune response?
Gout (gouty arthritis)
Nodular masses of monosodium urate crystals (tophi) may be deposited in soft tissue?
Chronic tophaceous gout