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26 Cards in this Set

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  • Back
Amino acids are a part of nutritional requirement. What is the result of hacing a PROTEIN MALNUTRITION?
Kwashiokor (swollen belly)
What is the result of a caloric deficiency?
What are the amino acids fed intravenously after surgery?
Glutamine and Arganine
What are the two major reactions for urea detoxification?
1.)Ammonia and Glutamic Acid-----> Glutamine (temporary)

2.) Ammonia w/ Urease to Urea and CO2.
Certain individuals require more amino acids than others. What are some of these examples?
Growing children, body builders and pregnant women have elevated needs of amino acids.
What are the nine essential amino acids?
What is the "special problem" with histidine and determining whether it is essential or not?
In some cases it is essential. Some histidine is made in the body in low concentration and it is often not enough. Nonetheless, it is not essential because it can be made.
Where is the histidine in the body coming from?
From CARNOSINE. Recall however that the carnosine was originally made from previously consumed histidine thus making it an essential amino acid.
What amino acid is said to be toxic?
Cysteine because it is highly insoluble and its build up can cause cysteine stones (kidney stones)
Amino acids including the essential amino acids can be made in the body if what is ingested? For what essential amino acids does this not work? For what other 2 amino acids does this not work? Why?
The body can make the amino acids if one ingests the alpha keto acid analog of the amino acid. It does not work for Lysine, Threonine, Proline and hydroxyproline because they do not have Aminotransferases.
What is the purpose and a problem with synthesizing amino acids as those above?
The purpose of the above reactions is to keep ammonia concentrations low.

1) it does not work for all including 2 essential amino acids.

2.) Alpha keto gluterates are toxic.
Only L Amino acids (and glycine) are used in protein synthesis. So what does the body do with a D Amino acid it consumes?
D Amino acid OXIDASE change D AA to the alpha keto analog and finally to the L- AA. Problem is it can only convert small concentrations.
What is the SPARING PHENEOMENA? Give 2 examples.
When some essential amino acids can be converted to NONessential amino acids.

Tyrosine from Phenylalanine
Cysteine from Methionine
If fed radioactive Carbon, what AA acids would you expect to be radioactively labeled? What are two problems?
All the nonessential AA should be labeled since they would use the C14 carbon.

1.) Tyrosine would not be radioactive because its carbons come from Phenylalanine (essential)

2.) Methionine becomes radioactive because it uses Cysteines carbon.
What is the first step in an aminotransferase reaction? ussually requires what vitamin?
Loss of the amino group. B6 complex.
The typical aminotransferase reaction is as follows:
AA1 gives NH3 to E-PLP which is now called E-PAP. E-PAP then transfers the NH3 group to the Alpha keto acid analog of another AA to give the Amino acid and the original E-PLP.

E-PAP + AKAA2 --> E-PLP + AA2
What are the important steps of Aminotransferase reactions, mechanistically?
The enzyme and the AA combine to make an Aldimine (Schiff's base) which undergoes a hydride shift and tautomerization to give a KETAMINE.
All Aminotransferases are what kind of enzynes?
They function on a Ping-Pong mechanism (bi bi). At least 2 half reactions.
What are 2 clinically important transaminases?
1.) SGPT- High concentration suggests liver problems. (transfers amine from GLU to ALA)

2.) SGOT- high concentration indicates liver problem. (Amine transfer from GLU to ASP)
Some Transaminases can even act on Carbons other than the alpha carbon. What is an example of this?
Ornitine + NH3 ---> GLN Semialdehyde
Besides aminotransferases what other CLASS of reactions are typical of AA? How is it different?
OXIDATIVE DEAMINATION. Here amino groups are still removed but by oxidation NOT transfers.
Give an example of a Oxidative Deamination. Note the equilibrium. What acivates/deactivates the reaction.
Glutamine deamination. Converts Glu to its alpha keto acid analog. Product favored. Activated by ADP and inhibited by ATP.
Oxidative deamination and Aminotransfer reactions can be coupled. What is the overall reaction. What can this lead to?
AA + H20 + NAD --> AKAA + NADH + NH4+

Always yields the AKAA of the AA. Problem is taht AKAA are toxic as is NH4. Further if those are high eq shifts to the left (away from AKG) so no TCA cycle energy.
Why is it that NH4 is so toxic in the body?
Amongst other things, it shifts equilibrium away from ATP production and does not allow the body to produce energy.
other than aminotransferases and oxidative deamination, what is another reaction of AA? What is the overall reaction?
Amino Acid Oxidases

AA + E-FMN ---> AKAA + NH3 +

E-FMNH2 + O2 --> E-FMN + H2O2
Finally some AA undergo hydration reactions. Give an example.
Serine ---> pyruvate
Threonine ---> AKetobutyrate