Amino Acid metabolism Flashcards
Why would we break down amino acids
Protein turnover
Protein rich diet
Starvation/uncontrolled diabetes
Are amino acids stored in the body?
No
How to we get amino acids
Dietary
Synthesized
Protein degradation
What are the two steps in catabolizing excess amino acids
Step1: Removal of Nitrogen (amino group)
Step2: Carbon skeleton
Where are free amino acids found
Cells
Blood
Extracellular fluid
What happens to amino acids in a low energy situation
Amino Acids are oxidized to make ATP
What happens to amino acids in a low glucose state
AA sent to liver and turned into glucose
What happens to AA in high energy/lots of glucose
AA sent to liver and turned into fat
What can AA be made into
ATP Glucose Fat Protein Nitrogen compounds
How many AA can muscles oxidize?
6
How many AA can the liver oxidize
20
What is AA oxidation
Break down of AA into ATP
What is an AA first broken down to during catabolism
Amino Group Carbon Skeleton (a-Keto acid)
What is the fate of the amino group of an AA
Urea and excreated
What is the fate of the carbon skeleton of an AA
ATP
Glucose
FA
What is the reaction that removes the Amino group of an AA? What enzyme is involved
Rxn: Transamination
Enzyme: Aminotransferases
What is the Amino group of an AA transfered to
A-ketogluterate
What are the reactants and products of Transaminoation
AA + a-ketogluterate
To
Keto acid + Glutamate
What is the importance of Glutamate in the body
It is used as a Amino Donor in bio-synthetic pathways
What determines the fate of a-keto acid
Energy charge Hormones Repiratory quotient Glucose concentration The tissue it is in
Where are most AA metabolized
The Liver
What transports AA to the liver
Glutamine
Alanine
What do you get when you combine Glutamate/Glutamine with a-ketoacid
a-ketogluterate (metabolite of krebs)
What do you get when you combine Alanine and a-ketoacid
Pyruvate (end metabolite of glycolosis)
What do you get when you combine Aspartate and a-ketoacid
Oxaloacetate (Kreb cycle intermediate)
Where is Glutamate produced? Where is Glutamine produced
Glutamate: Liver (AA–>a-ketogluterate–>Glutamate)
Glutamine: Extrahepatic tissues
What AA make up the highest concentration in the liver
Glutamine
Glutamate
Where is Glutamate in the liver transfered to in the liver
Cytosol to the mitochondria
What type of reaction removes the amino group off of Glutamate
Oxidative damination
What it produced from Oxidative deamination of Glutamate
NH4 (Ammonia)
a-Ketogluterate
What is the main transporter of Ammonia in the body
Glutamine
Glutamate+NH3–>Glutamine
How does muscle act as a Nitrogen donor
Muscle uses AA for Nitrogen to make Glutamine for export
What are the nitrogen donors in skeletal muscle
Leucine Isoleucine Valine Glutamate Aspartate Asparagine
What enzyme turns glutamate into glutamine in muscles
Glutamine synthetase
NH3+glutamate—>Glutamine
What enzyme hydrolyzes glutamine into glutamate
Glutaminase
Glutamine–>glutamate+NH3
What are the two systems that need nitrogen from gluatamine?
Digestive system
Immune system
How to skeletal muscles produce alanine
Muscles give amino group from glutamate to pyruvate –>Alanine
What enzyme transferes the amio group from glutamate to pyruvate
Alanine aminotransferase
What does Alanine aminotransferase differ in liver and muscles
Muscles: lots of pyruvate –> pushes rxn to make alanine
Liver: lots of alanine from muscles –> pushes rxn to make pyruvate
What is the steps in the muscles+liver of Glucose -alanine cycle
Muscles: Glucose –> Pyruvate –> Alanine –> Liver
Liver: Alanine –> Pyruvate –> glucose –> Muscles
What cycle is used to turn alanine into glucose in the liver
Gluconeogenesis
what percentage of energy does alanine provide during exercise
5%
Where do the carbons in alanine come from?
Mucles glycogen
What enzyme transfers the amino group from glutamate to oxaloacetate. What is formed
Enz: Aspartate aminotransferase
Prod: Aspartate
What is aspartate used for
Transporting Malate in and out of the mitochondria
What happens to excess nitrogen that is not used
liver converts it into urea and it is excreated
Why does nitrogen go to the liver
1) You have eaten too much protein
2) you are in gluconeogeneis
What are the two enzymes in the liver that are entry points for aa to be converted into urea
Glutamate dehydrogenase
Aspartate aminotransferase
What does the free NH3 in the liver need to be turned into in order to enter the urea cycle? What enzyme does it
Product: Carbamyol Phosphate
Enz: Carbamoyl Phosphatase
What is the first step in the urea cycle
Carbamoyl phosphate + L-Ornithine –> L-citrulline
What enzyme is used in the first step of the urea cycle
Ornithine transcarbamoylase
What is the second step in the urea cycle
L-Citrulline –> Argininosuccinate
What enzyme is used in the second step of the urea cycle
Argininosuccinate
What AA provides a second nitrogen during the second step of the urea cycle
Aspartate
What is the third step in the urea cycle
Argininosuccinate –> L-arginine
What enzyme is used in the third step of the urea cycle
Arginiosuccinate lyase
What is a by-product of the third step of the urea cycle
Fumarate
What is the 4th step of the urea cycle
L-Arginine –> L-ornithine
What step of the urea cycle produces urea
step 4
L-arginine –> L-Ornithine
What enzyme is used to turn L-arginine into –> L-Ornithine
Arginase
Where does some of the urea produced by the urea cycle diffuse into
GI tract and excreted in feces
How many nitrogens are on urea
2
One from aspartate
one from free NH3
What happens to the concentration of Glutamate and alanine in blood plasma during exercise
Glutamate = Decrease
Alanine = Increase
How much can ATP turn over increase during exercise. What does this mean for the cell?
100 fold
Kreb cycle intermediates need to increase 4-10 fold
What are the Branched Chain Amino Acids (BCAA’s)
Leucine
Isoleucine
Valine
What AA constitute 90% of muscles AA uptake after a meal
Leucine,
Isoleucine,
Valine
How much does glutamine release increase after a meal
It doubles
What amino acids are released in an amounts less than what is taken in
BCAA’s
Glutamate
Aspartate
Asparagine
What amino acids are released in an amount more than what is taken in
Alanine
Glutamine
What step of the urea cycle produces urea
step 4
L-arginine –> L-Ornithine
What enzyme is used to turn L-arginine into –> L-Ornithine
Arginase
Where does some of the urea produced by the urea cycle diffuse into
GI tract and excreted in feces
How many nitrogens are on urea
2
One from aspartate
one from free NH3
What happens to the concentration of Glutamate and alanine in blood plasma during exercise
Glutamate = Decrease
Alanine = Increase
How much can ATP turn over increase during exercise. What does this mean for the cell?
100 fold
Kreb cycle intermediates need to increase 4-10 fold
What are the Branched Chain Amino Acids (BCAA’s)
Leucine
Isoleucine
Valine
What AA constitute 90% of muscles AA uptake after a meal
Leucine,
Isoleucine,
Valine
How much does glutamine release increase after a meal
It doubles
What amino acids are released in amounts less than what is taken in
BCAA’s
Glutamate
Aspartate
Asparagine
What amino acids are released in amount more than what is taken in
Alanine
Glutamine
When are amino acids turned into glucose
Starvation
Low carb intake
Exercise
What two amino acids can not be turned into glucose
Leucine
Lysine
How are amino acids turned into fat
AA –> a-ketogluterate –> acetyl CoA
