Amino Acid Metabolism Flashcards
Where are the majority of amino acids metabolized?
Liver
What is the location of amino acid metabolism?
Liver and peripheral tissues
Are amino acids stored in the body?
No
How do we attain amino acids?
Diet and synthesis
Where can free amino acids be found?
Cells, blood, extracellular fluid
Do we have a larger amino acid pool or body protein?
Body protein
About how many grams of amino acids are in the amino acid pool?
100-200 grams
What percentage and amount of grams of protein can be found in the average 70 kg person?
15-20% or 12 kilograms
About what percentage of protein is found in the amino acid pool?
Less than 2%
About how much of the amino acid pool is found in intracellular skeletal muscle?
1/2
What type of transport system is used for amino acid transport?
Active transport systems (ATP)
Can the amino acid carriers be induced?
Yes
What can happen if a transporter ends up taking in a lot of one particular amino acid?
Intake of other amino acids can become limited
Are peptides or free amino acids more likely to be absorbed?
Peptides are absorbed better
Where are peptides specifically broken down into free amino acids for the blood?
Enterocytes
What must occur first to break down an amino acid?
Removal of the alpha-amino group (nitrogen)
The majority of nitrogen broken off of amino acids during the initial break down step becomes what compound?
Urea
Where does nitrogen broken off of amino acids get sent?
Liver for degradation
Can nitrogen be stored in the body?
No
Nitrogen is excreted from the body as what compound?
Urea
What are two reasons that nitrogen gets sent to the liver?
Too much protein has been eaten or for gluconeogenesis
Most amino acids transfer their alpha-amino group to what structure?
Alpha-ketoglutarate (amino acid acceptor)
What is the result of transamination?
Glutamate and alpha-keto acid
What is the required coenzyme for transamination?
Pyridoxal phosphate
Pyridoxal phosphate is a derivative of what vitamin?
Vitamin B6
What is transamination?
The transfer for the alpha-amino group of an amino acid to alpha-ketoglutarate
What enzyme is used for transamination?
Aminotransferases (transaminases)
What specific aminotransferase is used in muscle?
Alanine aminotransferase (ALT) aka glutamate-pyruvate transaminases (GPT)
What is the specific aminotransferase used in the liver?
Alanine aminotransferase (ALT) aka glutamate-pyruvate transaminase (GPT)
Exercising muscle produces a lot of what substance which pushes the reaction to make what final product?
Pyruvate, alanine
A lot of what substance coming from the muscle going to liver drives the reaction to product what final product?
Alanine, pyruvate
What enzyme transfers amino groups from glutamate to oxaloacetate?
Aspartate aminotransferase (AST)
Are aminotransferases extra or intracellular?
Intracellular
During oxidative deamination, what is released?
Ammonia group as free ammonia (NH3)
What is the location of oxidative deamination of glutamate?
Liver and kidney
What type of energy level stimulates oxidative deamination?
Low energy charge
The muscle primarily exports what two things to transport NH3 to the liver?
Glutamine or alanine
What is glutamine?
Glutamate + ammonia
What enzyme makes glutamine?
Glutamine synthetase
Can glutamate be transported freely in the bloodstream?
No because it’s toxic (therefore, glutamine is used)
Which specific amino acids may be the donors of nitrogen to make glutamine?
Leucine, isoleucine, valine, glutamate, aspartate, and asparagine (LIV GAA)
What process is heavily used for nitrogen excretion?
Urea cycle
What is the specific location of glutamate dehydrogenase?
Mitochondria (but know it’s primarily in the liver)
How does the liver “deal with” ammonia?
Makes urea out of it
What enzyme deaminates glutamate?
Glutamate dehydrogenase
What is the other name for aspartate aminotransferase (AST)?
Glutamate oxaloacetate transaminase (GOT)
What enzyme is prime for the entry point into the urea cycle?
Carbamoyl phosphatase
What substance is required in order for carbamoyl phosphate to be effective in the first step of the urea cycle?
ATP
Carbamoyl phosphate is used to move what substance to the liver?
The very first nitrogen
The second nitrogen involved in the urea cycle is a part of what substance?
Aspartate (in the citrulline reaction)
Urea is excreted from which organ?
Kidneys
Where are the two nitrogens from for each urea molecule?
One from free ammonia (NH3) and one from aspartate
What is the precursor for both nitrogens of a urea molecule?
Glutamate
What determines what happens to an alpha keto acid?
Energy charge, hormones (insulin or glucagon), glucose concentration, tissue (liver or muscle)
What happens to an amino acid with low energy charge?
It is oxidized to recreate ATP
What happens to an amino acid when there is low glucose?
Amino acid is sent to the liver to turn into glucose
Exercise has what effect on overall energy charge?
Creates low energy charge
What happens to amino acids during exercise?
Oxidized to make ATP in Krebs/ETC
What are the six amino acids that skeletal muscle is able to significantly oxidize?
Leucine, isoleucine, valine, glutamate, aspartate, asparagine
What pathway maintains blood glucose through gluconeogenesis?
Glucose-alanine cycle
Alanine provides about what percent of energy during exercise?
5%
Where did the carbons in alanine come from?
Muscle glycogen
Is there more glutamate intracellular or extracellular?
Intracellular (>50 to 1 ratio)
Moderate intensity exercise has what effect on alanine?
Increased concentration
What effect does low intensity exercise have on alanine concentration?
No effect
What effect does exercise have in glutamate concentration?
Decreased concentration
The demand for ATP requires what pathway to become much more active?
Krebs (to replenish ATP)
The breakdown of individual amino acids results in the formation of intermediates from which necessary pathway?
Krebs
What does anaplerosis mean?
The replenishment of Krebs intermediates that have been depleted
During exercise, does the glycolysis or Krebs pathway run faster?
Glycolysis
What is the source of pyruvate for exporting amino acids?
Muscle glycogen
What are branches chain amino acids primarily used for?
Fuel for the muscle
What amino acids make up over 90% of muscle amino acid uptake?
Leucine, isoleucine, valine (LIV)
Muscle is a prime donor of what substance?
Nitrogen
What enzyme hydrolyzes glutamine to glutamate to go back to the muscle?
Glutaminase
What specific are of the intestines constantly releases glutamate?
Splanchnic area
After a meal, there is a large uptake of what?
Branches chain amino acids (BCAA) and glutamate
The gut lacks sensitivity with uptake of what structure?
Branches chain amino acids
What is the primary site of amino acid uptake following a meal?
Liver
Which amino acids are released in amounts MORE than what is taken in?
Glutamine and alanine
Which amino acids are released LESS than what is taken in?
BCAAs, glutamate, aspartate, asparagine
What are the two most abundantly released amino acids?
Glutamine and alanine
Alpha ketoacids that have been turned into acetyl coA can also be turned into what?
Fat
Which two enzymes are eventually responsible for turning an amino acid into fat?
Acetyl coA carboxylase and fatty acid synthase
What is alpha ketoglutarate’s corresponding amino acid?
Glutamate
What is alanine’s corresponding amino acid?
Pyruvate
What is glutamate’s corresponding keto acid?
Alpha ketoglutarate
What is oxaloacetate’s corresponding amino acid?
Aspartate
