Unit II Amino Acid Metabolism Flashcards
With a low energy charge what will happen to an amino acid?
it is oxidized to get ATP
With low blood glucose, what will happen to an amino acid?
it’s converted to eneter gluconeogenesis to get glucose
What will happen to amino acid with a high energy charge and lots of glucose?
it’s converted in the liver for fat synthesis to make fat
Can amino acids be stored?
no
If an AA can’t be stored then what happens to it?
its broken down (catabolism)
What group is removed from an AA during catabolism?
an amino group
If an amino group is removed from an alpha carbon on an AA, what is produced?
alpha-ketoglutarate acid
What is the final product of amino acid catabolism when removing the amino group?
urea
What are the final products of AA catabolism when creating an alpha-keto acid?
ATP, Glucose, and Fatty acids
What is the main site for AA catabolism?
the liver
What does 50% of ATP production in the liver come from?
AA oxidation
Where are branched chain AA’s more often catabolized?
skeletal and cardiac muscle
What are the branched chain AA that the skeletal muscle is able to oxidize?
Leucine, Isoleucine, and Valine (LIV)
What are the other AA’s that skeletal muscle can oxidize?
Glutamate, Aspartate, and Asparagine (GAA)
All together what are the six AA’s that can be oxidized in the muscle?
LIV GAA
What is transamination?
the transfer of an amino group from one AA to an alpha-keto acid
What is deamination?
the removal of an amino group from an AA
What type of enzyme is associated with transamination?
aminotransferases, transaminases
What type of enzyme(s) is/are associated with deamination?
lyases, dehydratases, or dehydrogenases
What coenzyme is required for transamination?
pyridoxal phosphate
List some examples of aminotransferases
Alanine aminotransferase, and aspartate aminotransferase
What would be the result of an AA transfering its alpha-amino group to alpha-ketoglutarate?
glutamate and alpha-keto acid
Are transaminations reversible?
yes
In the oxidative demaination of glutamate, what would be the products?
alpha-ketoglutarate and and free ammonia
What is the enzyme used to deaminate glutamate?
glutamate dehydrogenase
What cofactor is coupled with glutamate dehydrogenase?
NAD+
What are alpha-keto acids also known as?
carbon skeletons
What are some examples of pathways that an alpha-keto acid may enter?
krebs, gluconeogenesis, and fat synthesis
What is the fate of ammonia?
excretion as urea
What is the alpha-ketoacid of alanine?
pyruvate
What is the alpha-ketoacid of aspartate?
oxaloacetate
What is the alpha-ketoacid of glutamine?
alpha-ketoglutarate
What is the alpha-ketoacid of glutamate?
alpha-ketoglutarate
How does an amino group make it into the mitochondria?
attached to glutamate
Once an amino group is in the mitochondria as glutamate, what then happens to that amino group?
it is excreted or transfered to an alpha-ketoglutarate to be used in other metabolic pathways
Ammonia in extrahepatic tissues is transported to the liver in what form?
glutamine
What enzyme is used to stick an extra amino group on glutamate?
glutamine synthetase
Does glutamine synthetase require energy?
yes, ATP
How is muscle a nitrogen donor?
by stealing amino groups, taking their nitrogen, and creating glutamine
What enzyme in the muscle turns glutamate into glutamine?
glutamine synthase
What does glutamine synthase add ti glutamate in the muscle?
nitrogen
In the muscle, what turns glutamine back to glutamate?
glutaminase
What is the alpha-ketoacid of alanine?
pyruvate
In skeletal muscle, what makes alanine from pyruvate?
alanine aminotransferase (ALT) or glutamate-pyruvate transaminase (GPT)
In exercising muscle a lot of pyruvate is created, what would this push the reaction towards?
the making of alanine
In the liver a lot of alanine is coming skeletal muscle, what would this push the reaction towards?
making pyruvate
What enzyme transfers an amino group from glutamate to oxaloacetate to make aspartate?
aspartate aminotransferase (AST) or glutamate oxaloacetate transaminase (GOT)
What transport shuttle is aspartate used in?
the malate-aspartate shuttle system
What is the nitrogen from aspartate donatedto?
for purines/pyrimidine synthesis or used inthe urea cycle
If nitrogen isn’tbeing usedfor synthesis,what happens to it?
it is excreted through to urea cycle
List a couple of reasons why liver may be getting lost of nitrogen
Eaten to much protein, GNG, exercise, starvation, and no carbs in diet
Glutamine can transfer nitrogen to the liver, what enzyme places an amino group on glutamate to make it into glutamine?
glutamine synthase
Besides glutamine, what else can transport nitrogen to the liver?
alanine-glucose cycle
What does the first NH3 on urea come from?
from glutamate dehydrogenase (GDH)
How does glutamate dehydrogenase create an amino group?
via oxidatative deamination of glutamate
Where does the second NH3 on urea come from?
from aspartate aminotransferase (AST)
How does AST create an amino group for urea?
it transfers amino groups from glutamate to oxaloacetate, which forms aspartate
What is the alpha-ketoacid of glutamate again?
alpha-ketoglutarate
What enzyme would create carbamoyl phosphate from CO2, NH3, and 2 ATP?
carbamoyl phosphatase
Where in the cell is carbamoyl phosphatease active?
the mitochondrial matrix
What two places in a cell does the urea cycle take place?
the cytosol and mitochondrial matrix
What can be considered the prep step of the urea cycle?
carbamoyl phosphtase
Carbamoyl phosphate combines with L-ornithine to create?
L-citrulline
What enzyme catalyzes the reaction that creates L-citrulline?
ornithine transcarbamoylase
What compound adds the second NH3 in the urea cycle?
aspartate
Aspartate combines with citrulline to create?
Argininosuccinate
What enzyme catalyes the formation of argininosuccinate?
argininosuccinate synthase
What enzyme catalyes the creating of arginine?
argininosuccinate lyase
A by product of the creation of arginine is?
fumarate
What enzyme cleaves off two amino groups to create urea?
arginase
What enzyme catalyes the formation of ornithine?
arginase
What is the compound that is the precursor for both amino groups donated to make urea?
glutamate
Once glutamate dontes an amino group to oxaloacetate, what is formed?
aspartate
If there is a low energy charge in the cell, what happens to an amino acid?
its oxidized to make ATP
If blood glucose is low, what happens to an amino acid?
it is converted to enter gluconeogenesis to make glucose
If there is a high enery charge and lots of glucose, what happens to an amino acid?
it is converted in to liver to be used in fat synthesis
What are the 6 amino acids that skeletal muscle can metabolize?
LIVGAA
During carbohydrate, fat, and protein burning, what are amino acids shipped to the liver on what compound?
alanine
Alpha-ketoglutarate entering krebs cycle can be called what process?
anaplerosis
What does anaplerosis mean?
Adding substrates from another metabolic process
During exercise, having glycolysis run faster does what for amino acid metabolism?
to make extra pyruvate for picking up amino acids being oxidized in muscle
An increase in pyruvate in the muscle during exercise aslo creates an increase in what else?
alanine to get nitrogen to the liver
Glutamate concentrations in the plasma during exercise tend to?
decrease
Alanine concentrations in the plasama during exercise tend to what?
increase
SInce the muscle soaks up most BCAA’s and glutamate after a meal, how does the gut get AA?
the muscle exports glutamine to feed the areas that need it
What are the 3 BCAA used by muscle?
Leucine, Isoleucine, and Valine
What is over 90% of muscle amino acid uptake?
LIV and glutamate
Muscle amino acid is released in lower amounts because?
its being used
What are the most abundatly released amino acids?
Glutamine and alanine
Glutamine and alanine are considered to be transporters, true or flase?
true
List some conditions that would stimulate GNG from AA
low carbs, exercise, fasting, etc
What are the only ketogenic AA’s?
leucine and lysine
Describe how an AA can be made into fat?
AA to alpha-ketoacid into Acetyl-CoA then fatty acid
