amino acid catabolism

Question 1

% of energy intake from CHO, proteins, fat

Answer 1

Fat: 
18 and moins: 2004= 30.6 2015=30.9
18 et + = 31.3 , 32.3
Protein: 
18 et moins: 2004=14.6, 2015=15.6
18 et +: 16.5 , 17
Carbohydrate: 
18 et moins : 2004=2004 54.6 , 53.4
18 et +: 49.1 , 47,7

Question 2

4 important AA in nitrogen metabolism

Answer 2

4 AA that are converted into TCA cycle intermediate:
1. Glutamate and glutamine are converted into a-ketoglutarate
** they are very important, they act as a kind of general collection points for amino groups
2. Alanine to pyruvate
Aspartate to oxaloacetate

Question 3

transamination reaction (Amino group in liver and other tissues) + 4 characteristics

Answer 3

** transamination= enzymatic transfer of an amino group from an a-amino acid to a a-keto acid

1. First step after the L-amino acids arrive in the liver is the removal of the a-amino groups by aminotransferase which is transferred to the a-carbon atom of a-ketogluatarate, leaving behind the a-keto acid
* * no loss of amino groups in these reactions, because the a-ketoglutarate  becomed aminated as the a-amino acid is deaminated * * the goal is to collect the amino groups from many different AA in the form of L-glutamate. The glutamate then functions as an amino group donor for biosynthetic pathways or for extrection pathways that lead to the elimination of nitrogenous waste products

1. A-ketoglutarate = general amino acceptor
2. No net loss of amino groups
3. Aminotransferase are AA specific (ex: alanine aminotransferase) 4. PLP acts as cofactor for these enzymes (recall: glycogen phosphorylase)

Question 4

deamination : where? which enzyme? what happen?

Answer 4

in the mitochondria
- glutamate: amino group donor for extrection and biosynthetic pathways

** before= amino groups of a-AA are collected in the liver in the form of L-glutamate molecules but these amino groups must be removed from glutamate to prepare them for the exctrection
So, glutamate is transported from the cytosol to the mitochondria where it undergoes oxidative deamination catalyzed by L- glutamate dehydrogenase (present in the mitochondria)
** L-glutamate dehydrogenase can use NAD+ or NADP+ as cofactor
** product = a-ketoglutarate where it can be used in the TCA cycle, transamination or gluconeogenesis

Question 5

transport of ammonia from other tissues

Answer 5

Excess ammonia in tissues is added to glutamate to form glutamine, a process catalyze by glutamine synthetase (use ATP). After transport in the bloodstream, glutamine enters the liver and NH4+ is liberated in the mitochondria by enzyme glutaminase

• • glutamine= nontoxic transport form of ammonia ; present in blood in much higher concentrations than other AA
• The amide nitrogen is released as ammonium ion in the mitochondria where the enzyme glutaminase converts glutamine to glutamate and NH4+. NH4+ from intestine and kidney is transported to the liver in the blood. In the liver, the ammonia is disposed by the urea synthesis