AA breakdown Flashcards
two main themes of AA catabolism
catabolism of amino groups (N theme)
catabolism of carbon skeletons (C theme)
catabolism of amino groups (N theme)
amino group deamination> detoxification of ammonia
catabolism of carbon groups (C theme)
broken down to critic acid cycle intermediates> 20 dif pathways
enzymatic degradation of dietary proteins
starts in stomach
-polypeptide chains broken into smaller peptides
small intestinie
-free AA transported through epithelial cells and anter blood capilaries to travel to liver
essenstial AA
nine and must be broken down from protein in our diet
when is protein broken down
during protein turnover or when carb fuel not availabel
what happens when amine group is separated during metabolism (as ammonia)
it can be toxic to the cell
what must happen to prevent amomonia toxicity
- ammonia must be removed from AA
- ammonia must be sent to liver to be metabolized into less toxic substance (urea)
where does glutamine come from
muscle and other tissues
where does alanine come from
muscle
energy of transamination reactions
reversible and delta G is zero
what do transaminases do
move Amino group from AA to keto acid (a ketoglutarate)
require a cofactor pyridoxine (vit B6)
what shuttle relies on transaminases
malata aspartate shuttle
differences bw transaminases
differ in specificity for the L amino acid
- many specific for a ketoglutarate as amino group acceptor
-reactions effectively collect amino groups from many AA in the form of L glutamate
PLP long version
pyridoxine/ pyridoxal phosphate
PLP, what is it and what does it do
used as prosthetic group by all aminotransferases
carries amino groups to active site
transfers amino group to a-keto acid
PLP and other enzymes
transamination
racemization
decarboxylation
what does glutamate release its amino group as and where
ammonia in the liver
wehre does NH4 in the mitochondria come from
many different a-amino acids in the form of amino group of L-glutamate or amide nitrogen of glutamine
glutamate oxaditative deamination
doesnt have to transfer its nitrogen group bc it can undergo oxidative deamination in the mitochondrial matrix as ammonia in the cytoplasm woudl damage cell
this rxn is catalyzed by L-glutamate dehydrogenase
what does L glutamate dehydrogenase use
NAD+
L glutamate dehydrogenase
produces a-ketoglutarate to enter CAC or glucose synthesis
produces NH4 to enter urea cycle
transdeamination
overal reaction of transmination and glytamate dehydrogenase
