Metabolic fate of Amino Acids Flashcards
what are the 9 essential amino acids
PVT TIM HLL
What makes up an amino group
alpha carbon, R group, carboxyl group, amino group, hydrogen
what goes into an amino acid pool
Body proteins (turnover), dietary proteins (after digestion), Synthesis in the liver (non-essential only)
what comes out of an amino acid pool
anabolism and catabolism
what is produced in anabolism
- Endogenous proteins e.g. enzymes, hormones, milk, muscle
- Other nitrogenous compounds e.g. neurotransmitters
what is produced in catabolism
- alpha-keto acid (glucose, ketone bodies, CO2, H20, energy)
- urea
what process produces carbohydrates
glycolysis
what process produces protein
AA catabolism
what process produces fat
fatty acid oxidation
what is it called when Input to the amino acid pool should match its output
nitrogen balance
What is the purpose of amino acid degradation?
- to supply energy
- to supply intermediates for the synthesis of other important compounds
- to remove amino acids that in excess amounts could be toxic / harmful
where does amino acid degradation take place
in the liver and is a 2-stage process
what occurs in stage 1
the α-amino nitrogen must be removed (via transamination and oxidative deamination reactions) – amino group eventually ends up as urea
what occurs in stage 2
remaining carbon skeletons are then shuttled into central metabolic pathways (eg. Citric acid cycle)
what is Transamination
the transfer of an amino group firstly to a keto acid to form new amino acids
what is Aspartate transaminase (AST)
AST catalyses the interconversion of aspartate and α-ketoglutarate to oxaloacetate and glutamate
AST is a commonly used as a clinical diagnostic test for liver function
what is Alanine transaminase (ALT)
Alanine transaminase (ALT) catalyses the interconversion of alanine and α- ketoglutarate to pyruvate and glutamate
ALT useful for screening for liver-associated problem
what is Oxidative deamination
NAD+ is reduced to NADH and the amino acid is deaminated (amino group removed)
what happens to the ammonia
Transamination and oxidative deamination generate large amounts of ammonium ion
* Ammonium ions are extremely toxic and the body must be able to get rid of it
* Ammonium ions can be detoxified in the liver by their conversion to urea
* Urea cycle enables this process → urea excreted in the urine
who came up with the cyclic pathway
Krebs and Henseleit in 1932
what is the equation for the urea cycle
CO2 + NH4+ + 3ATP + aspartate + 2H2O —–> urea+2ADP+2Pi +AMP+PPi +fumarate+5H+
- Irreversible reaction
- requires in total 4 ATPs to form a single molecule of urea
- Cost of detoxification of ammonia is surprisingly HIGH!
what can The carbon skeleton of amino acids after deamination be used for
used in biosynthetic pathways or can be further degraded to produce energy
what are ketogenic amino acids
amino acids metabolised to acetoacetate or acetyl CoA > > ketone body formation
what are Glucogenic amino acids
amino acids metabolised to pyruvate or TCA intermediates > > gluconeogenesis
