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15 Cards in this Set
- Front
- Back
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Carbamoyl phosphate synthase I is located in the ____. CPS II is located in the ______. What amino acid regulates the activity of CPS I? Why?
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mitochondria; cytosol. Arginine, because arginine is required for the formation of N-acetylglutamic acid (Arg provides positive feedback)
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Does CPSI require ATP?
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Yes; 2 ATP.
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Ornithine transcarbamoylase (OTC) condense which two molecules? What is formed as a result?
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Carbamoyl phosphate (a phosphate group is donated) and ornithine (shuttled across the mitochondrial membrane), to form citrulline.
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Why is ammonia toxic at high concentrations?
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Reacts with alpha-ketoglutarate, an intermediate of the TCA, and halts TCA/oxphos at high concentrations.
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Argininosuccinate synthetase (AS) catalyzes the reaction of citrulline and what other amino acid? What other factor is required?
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Citrulline and Aspartate. ATP is required (AMP is produced)
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Why does the argininosuccinate synthase reaction ensure that the urea cycle moves forward?
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hydrolysis of PPi produced is irreversible
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Arginosuccinate lyase (AL, or argininosuccinase) cleaves argininosuccinase to form what two compounds?
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Arginine and fumarate. Thus, arginine is created for urea production.
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Fumarate, a 4C moeity, can be converted to glucose (glucogenesis) and what else?
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Malate, and then reoxidized to OAA into the TCA cycle.
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What is the formation of N-acetylglutamic acid regulated by?
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Arginine, an intermediate of the urea cycle.
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Therapy for urea cycle disorders include what? What amino acid is added?
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Low protein diet; add arginine. Use sodium benzoate and phenylacetyl CoA to encourage production of nitrogenous wastes: hippurate and phenyacetylglutamine.
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What are two excretion pathways which should be utilized in urea cycle disorders associated with hyperammonemia?
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hippurate and phenylacetylglutamine products
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What are polyamines for? What cofactors are required for their synthesis from ornithine?
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Since DNA is - charged, polyamines are required (+ charge) during DNA replication. Need decarboxylated SAM for synthesis of polyamines.
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Which three amino acids may be used for creatine synthesis?
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Glycine, arginine, methionine.
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What kinds of rxns are required for creatine synthesis, and where do they occur?
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Transamination (kidney), followed by methylation (liver).
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In the absence of ATP, muscle and brain tissue will reverse which pathway for ATP synthesis?
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Create creatine from creatine phosphate (using creatine kinase, a reversible enzyme)
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