Metabolism of amino acids, purine and pyrimidine bases Pavla Balínová.
Purine and pyrimidine catabolism
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Transcript of Purine and pyrimidine catabolism
PURINE AND PYRIMIDINE CATABOLISM
PURINE CATABOLISM
PURINE DEGRADATION
PURINE SALVAGE PATHWAY From normal turnover of cellular nucleic
acids Obtained from the diet Reutilization of adenine, hypoxanthine,
and guanineTwo enzymes:
1. Adenine phosphoribosyltransferase2. Hypoxanthine-guanine phosphoribosyltransferase
Hypoxanthine
Xanthine
Xanthine dehydrogenase
Allopurinol
GOUT
•Build up of hypoxanthine and guanine•Degradation of hypoxanthine and guanine results in increased uric acid•Absence of Hypoxanthine-guanine phosphoribosyltransferase.•Excess uric acid in urine often results in orange crystals in the diaper of affected children•Severe mental retardation•Self-mutilation•Involuntary movements•Gout
Lesch-Nyhan Syndrome
LESCH-NYHAN SYNDROME
PYRIMIDINE CATABOLISM
RIBONUCLEOTIDES TO DEOXYRIBONUCLEOTIDES
Very Important!
Guanine-Cytosine Adenine-Thymine
DNA Base Pairing
CHARGAFF’S RULE %A = %T and %G = %C In DNA, 1:1 ratio between purines and
pyrimidinesOrganism %A %G %C %T A/T G/C %GC %AT
φX174 24.0 23.3 21.5 31.2 0.77 1.08 44.8 55.2
Maize 26.8 22.8 23.2 27.2 0.99 0.98 46.1 54.0
Octopus 33.2 17.6 17.6 31.6 1.05 1.00 35.2 64.8
Chicken 28.0 22.0 21.6 28.4 0.99 1.02 43.7 56.4Rat 28.6 21.4 20.5 28.4 1.01 1.00 42.9 57.0
Human 29.3 20.7 20.0 30.0 0.98 1.04 40.7 59.3
Grasshopper
29.3 20.5 20.7 29.3 1.00 0.99 41.2 58.6
Sea Urchin 32.8 17.7 17.3 32.1 1.02 1.02 35.0 64.9
Wheat 27.3 22.7 22.8 27.1 1.01 1.00 45.5 54.4
Yeast 31.3 18.7 17.1 32.9 0.95 1.09 35.8 64.4
E. Coli 24.7 26.0 25.7 23.6 1.05 1.01 51.7 48.3
SUMMARY Purines: Uric
acid Reutilization of
adenine, hypoxanthine and guanine
End product: Urate (a.k.a.: Uric Acid )
Altered metabolism: Gout
Pyrimidines: Citric acid intermediates Acetyl-CoA derived
from Cytosine and Uracil degradation; Propionyl-CoA (Succinoyl-CoA) from Thymine degradation
Ammonia and CO2 Ring undergoes
complete degradation