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15 Cards in this Set
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Describe the enzyme, cofactor and products of the transanimase reaction.
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Enzyme: Aminotransferase
Cofactor: PLP (VITAMIN B6) α-amino acid: α-keotglutarate α-keto acid: Glutamate |
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Describe the role of glutamate dehydrogenase in donating NH3 for the urea cycle
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glutamate dehydrogenase gives a free ammonia to alanine in the muscles and then takes that ammonia back in the liver.
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List the reactions that form ammonia in the liver
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1. Transamination from alanine: (PLP)
2. Oxidative deamination from glutamate (glutamate dehydrogenase) 3. From Glutamine (glutaminase) |
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Describe ammonia formation in the gut
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Bacterial ureases form ammonia in the colon. In those with liver disease, this ammonia is not detoxified.
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Describe Hyperammonemia Type 1
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Deficiency: CPS I
Pathology: Hyerpammonemia, neurological Treatment: sometimes responds to Arginine to stimulate the formation of NAG which might stimulate CPS1. |
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Describe Hyperammonemia Type 2
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Deficiency: OTC (ornithine transcarbamoylase)
Pathology: Hyperammonemia, increased orotic acid in urine Treatment: ? |
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Describe Citrullinemia
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Deficiency: Argininosuccinate synthetase
Pathology: Hyperammonemia, ↑ citrulline levels Treatment: MAY include arginine to enhance citrulline excretion and provide high levels of substrate |
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Describe Argininosuccinic aciduria
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Deficiency: ASL (Argininosuccinate lyase)
Pathology: Hyperammonemia, ↑ arginino succinate levels Treatment: arginine for excretion |
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Describe Hyperargininemia
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Deficiency: Arginase
Pathology: ↑ arginine levels Treatment: diet of essential AAs excluding arginine. |
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What are the treatments for general Hyperammonemia?
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1. Dialysis
2. Benzoic acid - to help excrete glycine (1 N / molecule) 3. Diet (low protein/high carb) 4. Medication (a-keto acids) 5. Stress prevention 6. Liver transplantation |
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What role does benzoic acid fill in treating hyperammonemia?
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It is an amino acid scavenger.
It forms Benzoyl CoA which bonds with glycine to form Hippuratic acid. It takes 1 Nitrogen with it when excreted. |
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What role does phenylbutyrate fill in treating hyperammonemia?
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It undergoes beta-oxidation to form phenylacetate which degrades to phenylacetyl CoA which combines with glutamine to form phenylacetylglutamine which takes 2 nitrogens with it when excreted.
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What role does argenine fill in treating hyperammonemia?
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It stimulates the formation of NAG which MIGHT stimulate deficient CPSI.
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Describe Acquired hyperammonemia
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Cause: Liver disease, cirrhosis
Pathology: Portal blood enters the systemic circulation without going to the liver. Treatment: 1. Low protein/high carb diet 2. Lactulose which bacteria can't digest in gut 3. Neomycin (antibiotic to kill gut bacteria making lactate) |