amino acid degradation Flashcards
Can all animals synthesize all the amino acids?
No, not all organisms can make all the aa (some plants and bacteria can). many
What determines the nutritional quality of the amino acid?
the more closely the amino acid compostion of the ingested protein resembles the aminal eating the protein => the higher nutritioanl value. For humans, mammalian protein is the highest nutritional quality
When determining the type of fat, what factors should u take into account
Protien, sugar, the amoutn of saturarted fat
What should u keep in midn when it comes to nutirional value?
Its not just abotu the quantity, but also the compositions
What are essential aa?
Amino acids that cannot be produced by the body and must be preesent in the diet.
What are conditionally non-essential amino acoids?
Can be produced by the body ,but at rates lower than certain conditional requirements. They are essential at certain times only
What are non-essential amino acids?
can be produced by the body. not required as part of the diet.
Can you replace 1 g of animal protein with 1 g of plant protein?
No because the amino acid compsiiton of the 2 would differ
How do cows milk and soy milk compare?
Similar aa composition, but differe on which amino acids are most limiting. Both are great protein sources for adults, but neither is good enough for nfnats
What is excess amino acids used for?
No glycogen equivalent
- building blocks for protein synteheiss and nucleotide syntheiss
- can be converted into glucose or TAG -> used to suppky energy
Why is dietary protein important?
because humans cannot syntheized all of the amino acis
What breaks down proteins?
Proteases
What breaks down lipids?
Lipases?
What breaks downn starch?
amylase
How does the stomach digest protein?
The highly acidic envrionemtn denatures the protein, making them more suscueptible to digestion by proteolytic enzymes.
Pepsin breaks the protein down into smaller peptides and amino acids.
The acid enviornment is generated by K/H ATPase
How can excesive acid generation result in reflux be treated?
Treated by inibitos of the K+/H+ ATPase such as omeprazole
How is protein digested in the intestine
Protein is digested into small amino acids and oligopeptides. the amino acids are transported by transporters across the intestinal cell.
peptidasss on intestinal cells cleave the ologiopeptides into tri or di peptides -> transport into the intestinal cells and are degarded into amino acids
the amino acids are transported thorugh the blood by antiporters
What is the fate of amino acids when proteins are degraded?
N: excess N is elimated as urea
C: recycled (anabolism/catabolsim
What is Nh4+
ammonium
What is NH3
Ammonia
What is urea
CO(NH2)2
How does chewing affect digestion?
impact on protein digestion and adsorption rate
What is transamination?
Removal of N from amino acids
what type of compound forms after removal of N from amino acids?
alpha keto acid
Whats the amino acid for pyruvate?
Alanine
Whats the amino acid for Oxaloacetate?
Aspartate
doner
How is pyruvate -> alanine
pyruvate + glutamate -> alanine aminotransferase -> allanine and alpha ketoglutatrate
How is OAA -> asparate
OAA + glutamate -> asparateate aminotransferase asparate + alpha ketoglutarate
Do all amino acids use glutamate dehydrogenase?
No, because serine nad threonien can be directly converted into NH4+
What are the steps about how alpha amino groups are converted into ammonium?
- Aminotransferase.
Trnasfers an amino grop from an amino acid to alphoa ketoglutarate into glutamate
- oxidative deamination
(liver specific enzyme, locaged in the mt)
glutamate dehydrogenase.
catalyzes oxidative deamination, renergerting alpha ketoglutarae and procing ammonium and NADH.
Reactions catalyzed by aminotransferases can be used for
syntehsis and degrdationof amino aicd
glutamate dehydrogenase is onluy found in
the liver, locaed in the mitocjonidra
What markers are a sign for muscle damage, aka. What levels change after exercising or in a car accident where the body experiences a lot of stress
Alanain aminotransferase
asparate aminotransferase
creatine kinase
What are high ALt and AST blood levels a sign of?
Muscle damage
liver damange -> leaky anzyme
What are branched chain amino acids? what make them special?
They are essnetial amino acids (our bodies cnanot synthesize them). Play a unique role in muscle tissue.
BCAA unlike other amino acids are not broken down in the liver. -> contribute to energy metbaolism during exercse
What are brnaced chain aa?
Leucine (L), Valine (V), isoleucine (IIe)
How does branced chain amino acids differ between liver and muscle?
Liver cannot deaminate branched chain amino acids
Muscle: can use bracnched chain amino acids for energy
Talk about the BCAA deamination in muscles and how its used for energy (5 steps)
`1. Removal of ammonium ion from BCAA (however, muscles lack this enzyme of the urea cycle) -> ammonium must be released in a form that can be absorbed by the liver and converted into urea.
- Ammonium from BCAA is transfered to pryvate by alanine aminotransferase -> making alaminine. (transamination)
Alananine made in the muscles is released into the blood.
- The liver takes up alanine and converts it back into pyruvate via alanine aminotransferase (transmination)
- The pyruvate is then used for gluconeogenesis
- and the amino group (originally from BCAA) is used in the urea cycle in the lier.m
What happesn to the carbon in BCAA?
Leucine, isoleucine -> converted into acetyl coA for energy
isoleucine val -> converted into succinyl coA
What are the 2 ways BCAA generate energy?
from pyruvarte from the cori cycle pt 2.
from the carbon backbone of branched chain amino acids
Summary of the urea cycle
NH4+ combines with Co2 resulting in urea and water.
Urea is elimiated through the kidney and in urine.
During the cycle, intermediates of the TCA are produced
What are the different organs that do nitrogen disposal in the body?
Liver is the main, followed by the kidney
What comparments do the urea cycle?
Mitochondria and cystosol
what is the anaeplerotic reaction in the urea cycle?
Production of fumerate
What enzymes are needed for the urea cycle and what compartments are they in?
Mitochondria:
A. Formation of carbamoyl phosphate.
Carbamoyl phosphate synthase I
B. Formation of citrulline
Ornithine transcarbamoylase
Cytosol
C. Formation of argininosuccinate
Argininosuccinate synthetase
D. Formation of arginine
Arginiosuccinase/ lyase
E. Formation of urea
arginase
How much ATP is required to run 1 urea cycle?
- 2 ATP in the mitchondria to make carbamoyl phosphate
2 ATP in the cytosol to make arginosuccinate (from aspartate and citrulline)
Explain the urea cycle
- Urea cycle begins in the mitchondrial matrix. HCo3 and Nh4 combine to form carbamoyl phosphate catalyzed by carbomoyl phosphate synthetease I. (require 2 ATP)
- Ornithine serves as a carrier that will recieve the nitrogen atom and form citrulline.
- A second nitrogen atom comes from asparate, with citrulliine, forming arginosccuinate (consumes 2 ATP)
- Argininosuccinate is cleaved forming arginine and fumarate.
- arginine is cleaved to regenerated ornithine and urea.
What types of transport must happen for the urea cycle?
transport of ornithine from the cytosol to the mitochondria
transport of citrulline from mt to cystol
How energy consuming is the process of making urea?
Adults produce ~ 30 g of urea each day. this process consumes up to 50% of the ATP produced in the liver.
What are some symptoms of elevated blood concentration of ammonia?
increase -> lead to disturbance of consciousness. A blood ammonium concertation higher -> coma and convulsions
How are the levels of urea different in aminals on high protein diets vs. aminamls in protein-free diets?
higher levels of urea cycle enzymes and CPS I in animals on high-protein diets and decreased in animals fed protein-free diets (long term regulation)
What is N-acetyl glutamate synthase? Where is it located?
A cofactor-producing enzyme. In the mitchondria
WHat are the different cofactors/enzymes/transporters involved in the urea cycle
5 catalytic enzymes:
1. carbamoyl phosphate synthetase I
2. ornithine transcarbamoylase
3. argininosuccinate synthetase
4. argininosccuinase/lyase
5. arginase
2 transporters:
citrin, ornithine transporter
1 co-factor producing enzyme:
N-acetyl glutamate syntetase (its in the mitchondria)
How is the urea cycle allosterically regulated
CPS 1 is allosterically regulated by N-acetyl Glutamate. CPS 1 requires NAG cfor acitivyt
N-acetyl glutamate is syntehzied from acetyl coA and glutamate by N-acetyl glutmate synthetase. NAG is made when glutamate is available -> sign that there is amino acid available
What would lead to an accumulation of ammonia?
Deficiency or absence of activity in CPS1, OTC, ASS1, ASL, or cofactor NAG
What are some treatments to lower ammonia?
dialysis, drugs, dietary protein restriction
What are the effects of excess NH4+
- Deletion of TCA intermediates (alpha keto glutarate, fumarate)
- Lead to ATP deficiency (TCA cycle not running)
in most urea cycle disorders, there is an accumulation of
Glu and Ala
Increase in glutamine, alamne, decrease in citrulline, ariginine
CPS1 defciinency
or OTC deficinecy
massive increase in critrbulline, decrease in arginine
argininosuccinate synthetase
Increasse in citrulline, increase in argininosuccinate, decrease in arginine
Argininosuccinase/lyase fienicycingy
increase in arginine
Arginase deficnicy
increase in glutamine, alanine
NAG definicey
What other disorders can lead to hyperammonia
Fatty acid oxidation disorder
Pyruvate carboylase definciey
How is the urea cycle linked to TCA and gluconeogensis
- Fumarate is turned into malate
- malate is oxidized into oxaloacetate
- Oxaloacetate has 2 fates:
- made into glucose by gluconeogensis
- transmination to make asparate and fuel into the urea cycle
How do bears face hibernation when it cannot excrete urea?
Gut microbiota changes with season. theres more during the winter months -> hekp with this
What pathways are providing bear with energy in the winter?
Lipid oxidation , reduced glucose utilization
Why is succinate higher in the winter for bears?
odd chain fatty acids?
Why is lactate lower in the winter for bears?
bc no glucose -> no fermentation
What types of amino acids are increased and decreased during the winter for bears?
- Increased levels of amino acids involved in the urea cycle
- decreased levels of glucogenic amino acids (they reduce their glucose usage
this is prob bc it takes a lot of energy to restore gluconeogensis)
How does the bacteria help the bears dispose of the nitrogen?
urea in bladder -> bacteria hydrolyze this -> make amino acids and proteins and bears utilzie this.
What happens to the carbon in amino acids?
they are converted into glucose or oxidized by the TCA cycle
What are some ketogenic amino acids?
Amino acids whose carbon skeletons are entirely or in part, degraded into acetyl coA or acetoacetyl coA.
What are glucogenic amino acids
Amino acids whose carbon skeleton can be converted into substrates for gluconeogenesis
Which maino acids are soley ketogenic?
leucine and lysine
Which amino acids are both glucogenic and ketogenic?
Thr, Ile, Phe, Trp, Tyr (5)
T I P T T
Threonine, isoleucine, phenylalanine, tryptophan, tyrosine
What does the degradation of aromatic amino acids require?
oxygenases
How do amino acids enter the TCA cycle
- can enter as pyruvate (via deamination, transmmination reactions
An increase in succinyl CoA could be due to?
Certain amino acids can make propionyl coA ->
oxidation of odd chain amino acids -> make succinyl coA
or from degradtion of odd chain fatty acids -> make succinyl coA
Accumulation of methylmalonyl coA is an indication of?
B12 deficinecy. Since cannot make succinyl coA from propionyl coA
What is phenylketonuria (PKU) ? Diagnosis? Therapy?
Caused by a deficiency/absence of phenylalanine hydroxlase (PAH). cannot make tyrosine from phenylalanine -> now tyrosine becomes an essential amino acids.
There is an accumulation of Phe in boildy fluid, smell. mentally retarted.
Diagnosis: Phe levels in blood, Phenylketone in urine.
Therapy: low Phe diet.
enzyme substiution not viable since it is. unstable
Why is the level of glucogenic amino acids in bears lower in the winter?
bc they are being used to make glucose
Why is there an increase in amino acids for the urea cycle in the winter?
bc bears are using it more.
for energy
and also to make glucose
