プリン塩基異化
Guanine deaminase
Short name=Guanase
Short name=Guanine aminase
EC=3.5.4.3
Alternative name(s):
Guanine aminohydrolase
Short name=GAH
p51-nedasin
- Function
- Catalyzes the hydrolytic deamination of guanine, producing xanthine and ammonia By similarity.
- Catalytic activity
- Guanine + H2O = xanthine + NH3.
- Cofactor
- Binds 1 zinc ion per subunit.
- Pathway
- Purine metabolism; guanine degradation; xanthine from guanine: step 1/1.
- Subunit structure
- Homodimer.
- Sequence similarities
- Belongs to the ATZ/TRZ family.
Xanthine dehydrogenase/oxidase
Including the following 2 domains:
Xanthine dehydrogenase
Short name=XD
EC=1.17.1.4
Xanthine oxidase
Short name=XO
EC=1.17.3.2
Alternative name(s):
Xanthine oxidoreductase
Short name=XOR
- Function
- Key enzyme in purine degradation. Catalyzes the oxidation of hypoxanthine to xanthine. Catalyzes the oxidation of xanthine to uric acid. Contributes to the generation of reactive oxygen species. Has also low oxidase activity towards aldehydes (in vitro). Ref.10
- Catalytic activity
- Hypoxanthine + NAD+ + H2O = xanthine + NADH; Xanthine + H2O + O2 = urate + H2O2.
- Cofactor
- Binds 2 2Fe-2S clusters. / FAD. / Binds 1 molybdenum-molybdopterin (Mo-MPT) cofactor per subunit. Ref.10
- Enzyme regulation
- Can be converted from the dehydrogenase form (D) to the oxidase form (O) irreversibly by proteolysis or reversibly through the oxidation of sulfhydryl groups By similarity. Ref.11
- Subunit structure
- Homodimer. Interacts with BTN1A1 By similarity.
- Subcellular location
- Cytoplasm By similarity. Peroxisome By similarity. Secreted.
- Tissue specificity
- Detected in milk (at protein level). Ref.11
- Post-translational modification
- Subject to partial proteolysis; this alters the enzyme from the dehydrogenase form (D) to the oxidase form (O) By similarity.
Contains sulfhydryl groups that are easily oxidized (in vitro); this alters the enzyme from the dehydrogenase form (D) to the oxidase form (O) By similarity.
- Involvement in disease
- Xanthinuria 1 (XU1) [MIM:278300]: A disorder characterized by excretion of very large amounts of xanthine in the urine and a tendency to form xanthine stones. Uric acid is strikingly diminished in serum and urine. Xanthinuria 1 is due to isolated xanthine dehydrogenase deficiency. Patients can metabolize allopurinol.
Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.7 Ref.8 Ref.12 Ref.13
Sequence similarities
Belongs to the xanthine dehydrogenase family.
Contains 1 2Fe-2S ferredoxin-type domain.
Contains 1 FAD-binding PCMH-type domain.
