2.10 Amino Acid Breakdown Flashcards
What enzyme catalyzes the first reaction in amino acid breakdown
Aminotransferases
What is the first step in amino acid breakdown
Removal of alpha amino group
Name the two important aminotransferases involved in the first step of AA degradtion
Alanine aminotransferase
Aspartate aminotransferase
What is the function of Alanine Aminotransferase
an amino group from alanine is given to alpha ketoglutarate to form pyruvate and glutamate
Function of Aspartate aminotransferase
Oxaloacetate recieves amino group from glutamate to produce aspartate and alpha-ketoglutarate.
This is the exception to the rule that glutamate receives an amino
What is the coenzyme of the aminotransferase reaction?
Pyridoxal Phosphate - B6
What happens to the remainder of the AA skeleton after degradation?
Carbon skeletons of alpha-ketoacids are used as intermediates in energy-producing metabolic pathway
What is the relationship between pyruvate and alanine
Alanine becomes pyruvate after it releases one of its amino groups
What is the relationship of alpha-ketoglutarate and glutamate
Alpha-ketoglutarate becomes glutamate when it gains an amino group
What is the relationship between oxaloacetate and Aspartate?
Oxaloacetate gains an amino group and becomes Aspartate
What is oxidative deamination and what amino acid undergoes this process?
Results in liberation of an amino group as a free ammonia
Glutamate is only amino acid to do this
What enzyme catalyzes oxidative deamination
Glutamate Dehydrogenase
Where is oxidative deamination found?
In Mitochondria of Liver and Kidney
What are the allosteric inhibitors of Oxidative deamination
ATP and GTP
What is the key reaction of the Urea Cycle and where does it occur?
HCO3, 2 ATP and Ammonium (from glutamate) –> Carbamoyl Phosphate
Occurs in mitochondrial matrix
What enzyme catalyzes the key reaction of the urea cycle
Carbamoyl Phosphate Synthetase I (CPS1)
What does Carbamoyl Phosphate Synthetase I require for activity
N-Acetyl Glutamate
Where does the Urea Cycle occur?
Liver mitochondria and cytosol
Where do the nitrogens in the urea cycle come from?
Ammonia comes from Glutamate and Aspartate
What is the ATP expense in the Urea Cycle
4 High energy phosphate bonds are broke
Where is Glutamine found in high concentrations?
Plasma
What enzyme catalyzes Glutamine giving its ammonia to become Glutamate in the liver
Glutaminase
Alanine is used to transport ammonia from where?
From muscle to liver.
Alanine travels to liver to react with what to form what?
It reacts with alpha-ketoglutarate to form Glutamate and Pyruvate
Describe how Aspartate adds its ammonium group to the urea cycle
It combines with Citrulline with the help of Argininosuccinate Synthase. This produces Argininosuccinate
How is Fumarate formed and why is it significant?
Argininosuccinate is cleaved to yield Arginine and Fumarate. Fumarate enters the CAC and links the two cycles together
Describe how fumarate and aspartate link the urea cycle to the CAC
Aspartate gives an ammonium molecule to Citrulline to make Argininosuccinate.
Argininosuccinate is cleaved to yield Arginine and Fumarate. Fumarate enters CAC and is oxidized to Oxaloacetate.
Oxaloacetate is then turned into Aspartate when given an Ammonium group
What causes Ammonia Toxicity?
A shift in Glutamate dehydrogenase towards Glutamate depletes alpha-ketoglutarate which causes toxicity
Describe the reaction and enzyme that is used to finally produce Urea
Arginine –> Ornthinine + Urea
Enzyme: Arginase
