31. Nitrogen Metabolism Flashcards
protein turnover is
300-400 g per day
amount of protein degraded and resynthesized from amino acids
protein turnover
sum of all free amino acids in cells and extracellular fluid
amino acid pool
sources of amino acid pool
- degradation and turnover of body protein
- dietary intake
- synthesis of nonessential amino acids
first phase of amino acid catabolism involves
•transamination -aminotransferase, pyridoxal phosphate
•oxidative deamination
-glutamate dehydrogenase
second phase of AA catabolism
- carbon skeletons of alpha keto acids converted to intermediates of
- glycolysis
- krebs cycle
excretion of excess nitrogen by humans as non toxic , water soluble urea
ureotelic
birds, who excrete uric acid as semisolid guano
uricotelic
seen in telostean fish, which excrete highlyy toxic ammonia
ammonotelic
Transamination of amino acids
enzyme and coenzyme
enzyme: aminotransferase
coenzyme: pyridoxal phosphate
all amino acids transfer their alpha amino group to alpha ketoglutarate –> glutamate
EXCEPT
Lysine
Threonine
Proline
Hydroxyproline
KTP + Hyp
- oxidative deamination of glutamate
L-glutamate –> alpha ketoglutarate
+ NH3
(glutamate dehydrogenase)
to release ammonia
glutamate +ammonia
requires this enzyme
glutamine synthase
glutamine is deaminated to release ammonia in 2 organs
and through what enzyme
liver - high protein intake
kidneys - response to metabolic acidosis
enzyme: glutaminase
In muscle, ammonia is released through
pyruvate transaminated to alanine
alanine -> liver -> pyruvate