Lecture 21 - Interorgan Amino Acid Catabolism Flashcards
The muscle metabolizes BCAA, resulting in excess release of _____ and ______.
- Alanine
2. Glutamine
BCAA are:
A. Essential
B. Non-essential
A
Where is glutamine synthase highest?
Muscle
Alanine synthesis in the ______ from pyruvate allows removal of ammonia without it being released as free ammonia.
A. muscle
B. liver
C. kidney
A - this process is catalyzed by transaminases
Alanine goes to the ____ where its amino group is incorporated into urea and the carbon skeleton is used for gluconeogenesis.
A. muscle
B. liver
C. kidney
B
What is the major metabolic fuel for intestinal cells?
A. glutamine
B. alanine
C. citrulline
A
What are the three branched chain amino acids?
- Valine
- Isoleucine
- Leucine
BCAAs undergo transaminination to a-keto acids. What enzyme catalyzes this reaction?
BCAA transaminase (BCAT)
BCAAs undergo oxidative decarboxylation to acyl-CoA. What enzyme catalyzes this reaction?
BCKA-DH
What are the two common reactions involved in BCAA catabolism?
- Transamination (to a-keto acid)
2. Oxidative decarboxylation (to acyl-CoA)
BCKAs can be used as fuel by:
A. Muscle B. Kidney C. Liver D. Brain E. All of the above
E
What is the principal enzyme involved in the mechanism for regulation of BCAA metabolism?
BCKA-DH
What is an identical gene product in BCKA DH, pyruvate DH, and a-ketoglutarate DH?
E3 subunit (dihydrolipoyl DH)
What cofactor is required for the conversion of propionyl-CoA to D-methylmalonyl-CoA?
Biotin
What cofactor is required for the conversion of L-methylmalonyl-CoA to succinyl-CoA?
B12
What enzyme catalyzes the conversion of D-methylmalonyl-CoA to L-methylmalonyl-CoA?
Epimerase
Both a-ketoglutarate DH and MCKA DH release what two products?
- NADH
2. CO2
What cannot be broken down as a result of carnitine deficiency?
Long-chain FAs
How does failure to break down long-chain FAs lead to hypoglycemia?
You have reduced energy for gluconeogenesis, so you have hypoglycemia.
How does hyperamonemia result from accumulation of proprionyl-CoA?
You’re tying up CoA molecules so in turn, you cannot run the urea cycle properly (need CoA to make NAG).
BCKA DH is inactive when ______ is phosphorylated.
E1
When protein is low in dietary intake, what is the impact on BCAA and BCKA?
A. BCAA are not conserved, so the BCKA is turned off
B. BCAA are conserved, so the BCKA is turned off
C. BCAA are conserved, so the BCKA is turned on
D. BCAA are not conserved, so the BCKA is turned on
B - this is a response to DIET, not hormones!
Increasing Vitamin B12 levels can (SOMETIMES) treat methylmalonic aciduria by increasing the activity of what enzyme?
Methylmalonyl-CoA mutase
Would someone with propionic academia want to increase or decrease their protein intake?
Restrict protein.
When will addition of cofactor Vitamin B12 do nothing to help methylmalonic aciduria?
If enzyme itself has a major defect or no functional enzyme can be synthesized, the addition of a cofactor will do nothing to help.
What enzyme is deficient in cases of methylmalonic aciduria?
Methylmalonyl-CoA mutase
Maple Syrup Urine Disease is a deficiency in ____________.
BCKA DH
If an enzyme is in a _______ pathway, phosphorylation activates it.
catabolic
If an enzyme is in an anabolic pathway, phosphorylation ________ it.
inhibits
What is the treatment for maple syrup urine disease?
No BCAA in diet initially and then supplement to maintain normal concentrations.
