Nitrogen Metabolism Part 1 Flashcards
What is the first step in the Catabolism of amino acids?
Separation of the amino group from the carbon skeleton.
Transamination reaction (removing amino group from carbon skeleton) requires what coenzyme?
Pyridoxal Phosphate
Acquired hyperammonemia
Hepatitis, liver ischemia, hepatotoxins, and cirrhosis.
Hereditary hyperammonemia
Genetic deficiencies of any of the five enzymes of the urea cycle.
Role of Alanine aminotransferase?
Enzyme that transfers amino group from Alanine to a-ketoglutarate, resulting in pyruvate and Glutamate.
Role of Aspartate aminotransferase?
Enzyme that transfers amino group from Aspartate to a-ketoglutarate, resulting in Oxaloacetate and Glutamate.
Role of Pyridoxal phosphate (PLP)
Coenzyme of aminotransferases.
Role of Glutamate dehydrogenase?
Enzyme that drives Oxidative Deamination
What electron acceptors are used for Oxidative deamination?
NAD+ or NADP+
Explain the regulation of Glutamate dehydrogenase activity?
- Allosterically regulated:
- ADP and GDP increase activity
- ATP and GTP decrease activity.
Ketogenic Amino Acids (7)
- Form Acetyl-CoA:
- Leu, Ile, Thr, Lys, Phe, Tyr, Trp
Amino acids that can form either Ketogenic or Glucogenic Amino Acids?
Ile, Thr, Phe, Tyr, Trp
Glucogenic Amino Acids:
Which AA make pyruvate?
Ala, Cys, Gly, Ser, Thr, Trp
Glucogenic Amino Acids:
Which AA make a-ketoglutarate
Arg, Glu, Gln, His, Pro
Glucogenic Amino Acids:
Which AA make succinyl-CoA
Ile, Met, Thr, Val
Glucogenic Amino Acids:
Which AA make Fumarate?
Phe, Tyr
Glucogenic Amino Acids:
Which AA make Oxaloacetate
Asp, Asn
Where are branched amino acids metabolized?
Peripheral tissues (particularly muscle).
Describe the glutamate pathway?
- ATP and ammonia combine with glutamate to make glutamine.
- Uses Glutamine synthetase
- Travel to liver, and the process is reveresed.
Describe the glucose-alanine cycle?
- Glutamate is made by transamination, by transfering amino group to pyruvate.
- Done by alanine aminotransferase.
- Pyruvate is changed to alanine and sent to ther liver.
- Alanine then undergoes transamination and becomes pyruvate which is turned to glucose and shipped back to muscle.
What is the first nitrogen-acquiring reaction of the Urea cycle and what is the enzyme used?
- ATP + Bicarbonate —> Carbamoyl Phosphatase
- Carbamoyl phosphate synthetase 1
Regulation of CPS1
- Requires allosteric activation by N-acetylglutamate.
- The activator is synthed from Acetyl CoA and Glutamate, both increase after protein rich meal.
What role does Ornithine transcarbamoylase have in the urea cycle?
- Combines Ornithine and Carbamoyl phosphate into Citrulline.
What is the second nitrogen-acquireing reaction of the Urea Cycle?
- In Cytosol: Citrulline + ATP —> Argininosuccinate
- Argininosuccinate synthetase.
