Lecture 9 - Amino Acid Catabolism 2 Flashcards
What does high levels of glutamate cause?
Increased water in brain cells through osmosis, causing swelling of the brain leading to a coma
What is NH3 converted to and where does the conversion take place?
- Urea
- Liver
What do organisms need to have to produce urea from arginine?
Arginase
What are the 2 compartments of the urea cycle?
1) Carbamoyl phosphate acts as a carrier in the mitochondrial matrix
2) NH2 enters the urea cycle in the cytosol through the conversion of ornithine to citrulline
What is required to make urea?
2 NH3; one from glutamate and one from aspartate
Describe the asparate-argininosuccinate shunt
Argininosuccinate is split into arginine (which continues the urea cycle) and fumarate (which is converted to malate and then enters TCA cycle)
What can deficiencies in urea cycle enzymes lead to?
- Mental retardation (partial deficiency)
- Early death (mutation in both genes)
- NH3 build up
What can an NH3 buildup cause?
- Activation of glutamate dehydrogenase and glutamine synthetase
- Loss of ATP (decreases TCA cycle intermediates)
- Increase in glutamate
What is the treatment for a deficiency in urea cycle enzymes?
Low protein diet
What happens to alpha-keto acids?
They are ultimately converted in acetyl CoA that is used in TCA cycle
Generally describe the threonine/glycine/serine/alanine pathway
- Threonine is converted to acetyl CoA by 2 pathways
1) Threonine -> glycine -> serine -> pyruvate -> acetyl CoA
2) Threonine -> acetaldehyde -> acetate -> acetyl CoA
What can a deficiency in acetaldehyde dehydrogenase cause?
Alcohol intolerance
Which enzymes can convert alanine to pyruvate?
Alanine transaminase and alanine dehydrogenase
What is FH4?
- Tetrahydrofolate
- Can transfer one carbon in many oxidation states
What are the 3 oxidation states of tetrahydrofolate?
1) N5, N10-methenyl FH4
2) N5, N10-methylene FH4
3) N5-methy FH4