FINAL amino acid degradation Flashcards
Excess amino acids cannot be stored or excreted, and are instead processed to be used as metabolic fuels True or false ?
True
Where does the primary source for amino acid precursors that synthesize new cellular proteins ?
Dietary proteins
What are the primary fates of amino acids that are obtained from digestion of proteins?
Primary: synthesis of amino acids
Secondary : processed as metabolic fuels because the they are not excreted or stored
Protein injected in the diet are digested into what ?
Small peptides or free amino acids later on injected by intestine
Where does protein digestion begin?
Stomach
What about the environmental conditions of our stomach favor protein degradation?
Highly acidic which causes denaturation of diet proteins
What is the major digestive protease?
Pepsin
oligopeptides are results of?
The pancreatic proteases hydrolyzing the proteins into small fragments
digestion is completed by enzymes called?
peptidases that are attached to the external surfaces of the intestinal cells
What is the role of peptidases
When in relationship with obligo peptides?
These enzymes cleave the oligopeptides into amino acids and di- and tripeptides
What goes into the blood stream are single amino acids true or false?
True- after peptidases cleave the AA they are transported, the absorbed AA are released into the body by antiporters
The first step of entrance into the metabolic mainstream is
Remove amino group
Why must we remove the amino group?
Allow remainder of molecule to be converted into glucose , TCA intermediates or acetyl CoA
For mammals the major site of amino acid metabolism is ?
Liver
he polypeptide products of pepsin digestion stimulate the release of the hormone
CCK
effects of CCK hormone release?
The pancreas responds to CCK by releasing a host of digestive enzymes into the intestine, where the digestion of proteins continues.
Aminotransferase Enzymes Play an Important Role in the Catabolism of Amino Acid. One product of this reaction, regardless of the identity of the amino donor, is always the amino acid
glutamate
what catalyzes the transfer of an α-amino group from an α-amino acid to an α-ketoacid.
aminotransferase
Once glutamate has been synthesized from a transamination of α-ketoglutarate
the nitrogen atom is converted to an ammonium ion
oxidative deamination reaction of glutamate is catalyzed by
glutamate dehydrogenase
When glutamate is processed by glutamate dehydrogenase the resulting product is ?
Free ammonium ion and regeneration of a-ketoglutarate
Ammonium ion is a weak base and is cytotoxic at high concentrations. true or false?
false it is a strong base
Amino acids are processed?
liver
Is the liver the only location that is capable of amino acid degredation?
skeletal muscle- under special circumstances
peripheral tissue
For peripheral tissue and muscles why can the not process glutamate into urea ?
they lack the enzymes of urea cycle
Can the glucose alanine cycle happen in peripheral tissue?
no- it is used as a way to transfer ammonium from muscles into the liver
Where does glutamine synthesis take place ?
In peripheral tissue
During prolonged exercise and fasting, muscle uses branched-chain amino acids (Val, Ile, Leu) as fuel. The nitrogen removed is transferred (through glutamate). The resulting glutamate can then be used to transaminate what very common product of glycolysis?
pyruvate
Why is it significant that pyruvate was formed?
From pyruvate we are able to form alanine that can be transferred into the liver where it is transformed back into glutamate then secret ammonium as urea
Inside the liver, pyruvate can participate in gluconeogenesis to form glucose, which is released back into the bloodstream. The net reaction is the exchange of glucose for ammonium (in the form of alanine). how is this similar to the cori cycle?
This glucose-alanine cycle is conceptually similar to the Cori cycle, where lactate is exchanged for glucose.
peripheral tissues also contain the enzyme glutamine synthetase. This enzyme catalyzes the ATP- dependent synthesis of glutamine from free ammonium ion and glutamate. the results :
glutamine products can be secreted into the bloodstream- urea cycle
purpose of the urea cycle ?
package waste nitrogen in a water soluble form that can be readily excreted
where does the urea cycle take place ?
liver
What does the urea cycle start with ?
the formation of Carbamoyl phosphate
How is Carbamoyl phosphate formed?
cycle couples free ammonia (NH3) to bicarbonate (HCO3-) and synthesized by carbamoyl phosphate synthetase
carnbamoyl phosphate is simple and require little to non energy. true or false ?
False - it is energetically costly having 2 ATP’s consumed
carbamoyl phosphate contains an anhydride bond, and therefore has a high carbamoyl group transfer potential allowing it to couple with what ?
ornithine
The second reaction of the urea cycle is catalyzed by ……….., and results in the formation of …….. as follows:
- ornithine transcarbamoylase
- citrulline
The first and second reaction of the urea cycle happen specifically in ?
The mitochondrial matrix
Once formed, citrulline is transported into the ……, where it reacts with ……. in a reaction catalyzed by ……..
- cytoplasm
- aspartate
- argininosuccinate synthetase
The second reaction of the urea cycle requires ATP true or false?
true
The fourth reaction takes the product …… of the third reaction and uses ……….. to cleave into ……….
- Argininosuccinate
- Argininosuccinase
- Arginine and fumerate
What is the final step of Urea cycle catalyzed by
arginase.
The final yielded product of the urea cycle is ?
Urea and ornithine
What are the 7 end products resulting from the degradation of 20 major amino acids?
acetyl-CoA
acetoacetyl-CoA
pyruvate
α-ketoglutarate
succinyl-CoA
fumarate
oxaloacetate
What is the connection of the side product fumarate what was generated in the fourth reaction of the urea cycle?
fumarate can be hydrated to malate and serve as an intermediate of the TCA Cycle
Why does the urea cycle require so much energy?
It is costly because of the toxicity of ammonium ion
What would happen if you had a urea cycle that did not function correctly?
Any patient with a defect in the urea cycle will present clinically with elevated blood levels of ammonium ion.
If there is an overload of glutamate dehydrogenase reaction what could this mean?
Ammonia is the depletion of the TCA intermediate and causes a deficiency in ATP
Ketogenic definition
can give rise to ketone or fatty acids
gluconeogenic
can participate in gluconeogenesis
How do breakdown of amino acids and breakdown of fatty acids intersect
In a way they use the same enzymes but are modified just a bit
FAD-linked dehydrogenase and an ATP-dependent carboxylation to yield β-methylglutaconyl-CoA, this can be seen similarly in?
just like in fatty acid oxidation and acetyl-CoA carboxylase
Describe what inborn errors of metabolism are ?
Inborn errors of metabolism is when there is a hereditary defect in any of the enzymes. Thus compromising a particular pathway
Is it possible for inborn errors of metabolism to disrupt amino acid degradation?
yes- it is a one route typically
The diseases that deal with inborn error are autosomal recessive or dominant
dominant
Example of inborn errors of metabolism is maple syrup urine disease, what causes it?
deficiency in the branched-chain α-ketoacid dehydrogenase complex
α-ketoacids begins to accumulate
phenylketonuria is an example of what?
Inborn error of metabolism-absence - deficiency in phenylalanine hydroxylase causing a rise in the phenylalanine in the blood
