AA metabolism (14) Flashcards
(44 cards)
What are two pathological conditions that can cause ammonia toxicity?
- liver failure
2. metabolic diseases
What are the symptoms of ammonia toxicity?
irritability, vomiting, lethargy and confusion, respiratory distress, migraines
What does ketogenic mean?
amino acids are degraded to either acetyl coenzyme A or acetoacetyl coA
-these give rise to ketone bodies
Which amino acids are ketogenic?
leucine and lysine
What does glucogenic mean?
Amino acids that are degraded to pyruvate or CAC intermediates
How are the levels of glutamate, GABA, serotonin affected in ammonia toxicity
GABA and glutamate - decreased
Tryptophan - increased
What three amino acids are converted directly to pyruvate?
- Alanine
- serine
- cysteine
What enzyme converts alanine to pyruvate and what is the reaction type?
alanine transaminase - ALT
transamination of alpha-ketoglutarate
-important for liver function tests!
What is glycine converted into? What enzymes?
serine –> pyruvate
-serine hydroxymethyltransferase
or
into CO2 and free ammonia
-glycine cleavage enzyme
What cofactor does serine hydroxymethyltransferase use? What happens to the cofactor during the breakdown of glycine?
THF —> 5,10 methylene-THF
Why is the glycine –> serine –> pyruvate conversion reaction so important?
major source of one carbon groups in the body
What is threonine converted into?
to glycine –> serine –> pyruvate
Is the threonine breakdown reaction reversible or irreversible?
irreversible - duhh its an essential AA
What AAs are broken down into OAA?
Aspartate and aspargine
What enzyme breaks down aspartate ?
aspartate transaminase - AST
another marker for liver damage
Which AAs are converted to glutamate? how many carbons do these AAs have?
5 carbon AAs:
- arginine
- histidine
- proline
- glutamine
Which of these amino acids uses THF as a cofactor in it’s breakdown reaction: histidine, arginine, proline, glutamine?
histidine
Which amino acid is only essential during growth?
arginine
- need extra since the liver is constantly breaking it down to orthinine and urea
What amino acids are considered branched chain amino acids? what enzyme do these use for breakdown?
- valine
- leucine
- isoleucine
branched chain AA transaminase
What happens in mice that have branched chain AA trasaminase deficiency ?
- inc insulin sensitivity
- inc protein turnover
- inc serum leucine levels
- dec fat and body weight
- inc E expenditure
- looking into it as a weight loss product
BCATs breakdown branched chain AAs into what?
alpha-keto acids
What enzyme breaks down alpha-keto acids by oxidative decarboxylation? What are it’s cofactors?
brached chain ketoacid dehydrogenase
-TPP, Lipoamide, FAD, NAD
What is deficient in maple syrup urine disease? What happens as a result?
branched chain ketoacid dehydrogenase
-branched chain ketoaciduria
What are the treatments for maple syrup urine disease?
dietary restriction of branched chain AAs
- some will respond to thiamine!!
(branched chain ketoacid dehydrogenase uses thiamine as a cofactor)
