Amino acid catabolism Flashcards
3 situations in which amino acids are catabolised
-normal synthesis and degredation of proteins -when protein is in excess in the diet -during starvation
Ultimate purpose of amino acid catabolism
remove the amino group and use the carbon skeleton for TCA or to make gluconeogenic precursors to feed to the rest of the body
Where are amino acids processed ?
Liver`
What happens to the amino groups in amino acids when catabolised ?
They are either recycled, or converted and excreted
How are nitrogen groups from amino acid catabolism ‘passed around’ in the liver ?
They are added to α-ketogluterate to form glutamate (or glutamine). Glutamate is then sent to the liver mitochondria where it is given up and becomes NH4+
In the muscle, what happens to the extra amino groups ?
They are added to pyruvate in order to become alanine, which is transported to the liver
What converts pepsin to pepsinogen
The acid of the stomach
What happens to excess amino acids ?
they are NOT stored, they are either used for protein synthesis or used for energy The rest are excreted, which is why high protein diets put strain on the kidneys
Where does pepsin cleave ?
F,W,Y
What are the pancreatic proteases:
trypsin, chymotrypsin, carboxypeptidases A and B
Where do the pancreatic proteases cleave ?
they cleave short peptides into free amino acids
difference between ketogenic and glucogenic amino acids
Glucogenic amino acids make oxaloacetate to form glucose Ketogenic amino acids make acetyl CoA or acetoacetyl CoA to form ketones
amino groups are transformed into one of these three groups in this organ
they are turned into a non-toxic, water soluble product (urea, uriv acid, ammonium) in the liver
Transamino reaction
α ketogluterate + L-amino acid –> L-glutamate +α-keto group (catalysed py pyridoxal phosphate (PLP))
How is the amino group removed from glutamate in the liver ?
It uses glutamate dehydrogenase, which catalyses the oxydative deamanation of glutamate
NAD or NADP can be used under different conditions
How are pyruvate and alanine interconverted ?
In the muscle, pyruvate gets an amino group from glutamate and becomes alanine
This reaction is catalysed by alanine aminotransferase
The alanine is transferred through the blood to the liver, where the reaction occurs in reverse
(glucose-alanine cycle)