Nucleotide Metabolism Flashcards
What are purines and which nucleotides are purines?
Purines are heterocyclic aromatic organic compounds that consist of two rings fused together. The purines are adenine and guanine.
What are pyrimidines and which nucleotides are pyrimidines?
Pyrimidines are aromatic heterocyclic organic compounds. The pyrimidines are cytosine and thymine (DNA) and uracil (RNA).
What is Lesch-Nyhan syndrome?
Lesch-Nyhan syndrome is a rare X-linked recessive disorder that results in an almost complete absence of hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Lack of HGPRT results in the inability to salvage hypoxanthine and guanine, and the result is a build-up of uric acid. This in turn leads to de novo purine synthesis. The symptoms of Lesch-Nyhan syndrome are gout, severe intellectual disability, and self-mutilation.
What are the symptoms of gout and what is the treatment?
Gout is a disease of purine metabolism and salvage that results from build up of uric acid. The major cause is excessive purine synthesis leading to elevated levels of urate in the serum and deposits of urate crystals in joints of the extremities and kidneys. Treatment for gout utilizes the drug allopurinol, a base analogue of hypoxanthine. Allopurinol inhibits the enzyme xanthine oxidase, preventing the conversion of hypoxanthine to xanthine and xanthine to uric acid.
What is orotic aciduria and what is the treatment?
Orotic aciduria is a disease of pyrimidine metabolism that is caused by a deficiency in UMP synthase (the enzyme that catalyzes the conversion of orotic acid to UMP (uridine 5’-monophosphate). A deficiency in UMP synthase leads to megaloblastic anemia, which is characterized by large red blood cells. The treatment for orotic aciduria is uridine supplementation.
What is folate deficiency and how can it be rectified?
Folate deficiency is a deficiency in dihydrofolic acid (DHF) that can lead to the inhibition of dihydrofolate reductase, which prevents that formation of thymine. Folate deficiency can be rectified by supplementing the diet with folic acid (vitamin B9) or thymine.
What is a nucleoside analogue?
A nucleoside analogue is a molecule that resembles naturally occurring nucleosides and acts by causing termination of the nascent DNA chain. Nucleoside analogues are a large class of agents that include chemotherapeutic agents and antiviral agents.
Name common antiviral nucleoside analogues and what they are used to treat.
Acyclovir is used in the treatment of herpes virus infections. AZT (3’azido-2’3’-dideoxythymidine or zidovudine) is used in the treatment of HIV/AIDS.
