Lecture 9 - Valine Example Flashcards
Step 1
Valine -> alpha-keto isovalerate
Step 2
Alpha-keto isovalerate -> isobutyryl CoA
Step 3
Isobutyryl CoA -> methyl acrylyl CoA
Step 4
Methyl acrylyl CoA -> beta-hydroxy isobutyryl CoA
Step 5
Beta-hydroxy isobutyryl CoA -> beta-hydroxyl-isobutyrate
Step 6
Beta-hydroxyl-isobutyrate -> methyl malonyl semi-aldehyde
Step 7
Methyl malonyl semi-aldehyde -> propionyl CoA
Step 8
Propionyl CoA -> succinyl CoA
Enzyme for step 1
Branched chain amino acid-transaminase
Enzyme for step 2
Alpha-ketoacyl dehydrogenase
Enzyme for step 3
Acyl CoA dehydrogenase
Enzyme for step 4
Enoyl CoA hydratase
Enzyme for step 5
Beta-hydroxy isobutyryl CoA hydratase
Enzyme for step 6
Beta-hydroxy isobutyryl dehydrogenase
Enzyme for step 7
Methyl malonyl semi-aldehyde dehydrogenase
Enzyme for step 8 (3 enzymes)
1) Propionyl CoA carboxylase
2) Methyl malonyl CoA epimerase
3) Methyl malonyl CoA mutase
Cofactor for step 1
Alpha-ketoglutarate -> glutamate
Cofactor for step 2
- CoASH in
- NAD+ -> NADH + H+
- CO2 out
- TPP, FAD
Cofactor for step 3
FAD -> FADH2
Cofactor for step 4
H2O in
Cofactor for step 5
- H2O in
- CoASH out
Cofactor for step 6
NAD+ -> NADH + H+
Cofactor for step 7
- NAD+ -> NADH + H+
- CoASH in
Cofactor for step 8
None
What is alpha-ketoacyl dehydrogenase similar to with respect to cofactors?
Pyruvate dehydrogenase
What is important about the enzymes used for step 8?
They are used in fatty acid oxidation of odd-numbered chain fatty acids
What happens if alpha-keto acyl dehydrogenase is missing as a result of a genetic defect?
- The alpha-keto acids from valine, leucine, and isoleucine will accumulate in the blood and urine, impairing brain and nerve cell development
- Maple syrup urine disease
What happens after step 8?
- Succinyl-CoA is converted to oxaloacetate, which is then converted to pyruvate, then acetyl CoA, which then enters the TCA cycle
- Total process produces 4 CO2
