Urea cycle and its disorders

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Urea cycle and its disorders
R. C. Gupta Professor and Head Department of
Biochemistry National Institute of Medical
Sciences Jaipur, India
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E M B - R C G
EMB-RCG
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E M B - R C G
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E M B - R C G
EMB-RCG
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E M B - R C G
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E M B - R C G
EMB-RCG
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Transfer of amino groups to a-ketoglutarate
E M B - R C G
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EMB-RCG
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E M B - R C G
EMB-RCG
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Oxidative deamination of glutamate
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EMB-RCG
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Glutamate
a
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Transport of ammonia
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EMB-RCG
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E M B - R C G
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Synthesis of urea
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EMB-RCG
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Reactions of the urea cycle are

1. Synthesis of carbamoyl phosphate
2. Transfer of carbamoyl group to ornithine to form
   citrulline
3. Conversion of citrulline into argininosuccinate
4. Cleavage of argininosuccinate into arginine and
   fumarate
5. Hydrolysis of arginine into urea and ornithine

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E M B - R C G
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Transfer of carbamoyl group
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Conversion of citrulline into argininosuccinate
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Cleavage of argininosuccinate
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Hydrolysis of arginine
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Regulation of urea synthesis
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Hepatic encephalopathy
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Sterilization of gut by antibiotics is useful in
decreasing ammonia production by bacteria
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Low protein diet is also recommended to decrease
ammonia production
Administration of L-ornithine and L-aspartate is
useful in augmenting urea synthesis
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Lactulose is an indigestible and non-absorbable
disaccharide
It is given orally to convert ammonia into
ammonium ions in the gut
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Ammonium ions cannot be absorbed from the
intestines
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ATP deficit
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Increased level of GABA
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Decreased uptake of amino acids
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Inborn errors of urea cycle
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Disorder Deficient enzyme
Hyperammo-naemia, type I Carbamoyl phosphate synthetase
Hyperammo-naemia, type II Ornithine transcarbamoylase
Citrullinaemia Argininosuccinic acid synthetase
Argininosuccinic aciduria Argininosuccinase
Hyperargininaemia Arginase
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Thank you