Nucleotide Syn/Salvage Flashcards
Carbon sources of purine bases
Conversion of Ribose-5-phosphate
to PRPP
Comitted step in purine synthesis
Common precursor of AMP and GMP
IMP
Regulation of purine synthesis
Carbon sources of pyrimidine ring
Regulation of pyrimidine synthesis
Conversion of NDP to NTP
Orotic aciduria
Synthesis of dNDPs from NDPs
Regulation of ribonucleotide reductase
Pharm. targeting of deoxyribonucleotide synthesis
Purine Salvage
Catabolism of _______ leads to increased levels of urate
Purine catabolism
Causes of hyperurecemia and gout
Tx of gout
What leads to heriditary OA?
Lesch-Nyhan Syndrome
Defects in what two enzymes of the purine degredation pathway leads to immunodeficiency?
Megaloblastic anemia
What amino acid becomes essential in Pt’s w/ phenylketonuria (PKU)?
Tyrosine
Phenylalanine hydroxylase normally converts phe into tyr
What step in catecholamine synthesis requires B6?
DOPA decarboxylase catalyzes the conversion of L-DOPA to dopamine in the presence of the cofactor pyridoxal phosphate
B6 also found in cystathionine synthesis, heme synthesis, decarboxylation, and transamination reactions.
How does oraganic acidemia cause hyperammonemia?
By inhibiting the urea cycle
Also inhibits gluconeogenesis and promotes the oxidation of fatty acids to ketone bodies (results in ketotic hypoglycemia)
Alkaptonuria
Caused by a deficiency of homogentisate oxidase, an enzyme that converts homogentisate (HGA) to maleylacetoacetate. Affected individuals are usually asymptomatic in childhood but may excrete urine that turns dark if left standing (due to oxidation of accumulated HGA).
Eventually, HGA deposition in tissues throughout the body leads to connective tissue discoloration (e.g., bluish-black discoloration of ear cartilage and sclerae) and organ damage, with manifestations such as arthritis, nephrolithiasis, and coronary artery disease.
Treatment of alkaptonuria involves a diet low in tyrosine and phenylalanine, which reduces the formation of HGA.
