Corrin/B12 Biochemistry: Methylmalonyl-S-CoA Mutase Mechanism

The video explains the beta oxidation of odd-chain fatty acids, focusing on the conversion of propionyl CoA to succinyl CoA through a short catabolic pathway. It highlights the role of adenosylcobalamin, a derivative of vitamin B12, in the methylmalonyl CoA mutase reaction. The mechanism involves radical formation and hydrogen abstraction, ultimately leading to the production of succinyl CoA, which enters the TCA cycle. The video is part of a series on fat oxidation and B12 biochemistry.

What happens to a 17-carbon fatty acid during beta oxidation?

• It remains unchanged.

• It gains two carbons per cycle.

• It is reduced to a 15-carbon chain in the first cycle.

• It is converted into glucose.

What is the final product of the propionyl CoA catabolic pathway?

• Succinyl CoA

• Citrate

• Acetyl CoA

• Malonyl CoA

Which enzyme is responsible for converting propionyl CoA to D-methylmalonyl CoA?

• Acetyl CoA carboxylase

• Methylmalonyl CoA mutase

• Citrate synthase

• Propionyl CoA carboxylase

What is adenosylcobalamin a derivative of?

• Vitamin D

• Vitamin A

• Vitamin C

• Vitamin B12

What role does adenosylcobalamin play in the methylmalonyl CoA mutase reaction?

• It serves as a coenzyme.

• It inhibits the reaction.

• It acts as a substrate.

• It is a byproduct.

What is the initial oxidation state of cobalt in the methylmalonyl CoA mutase mechanism?

• 0

• 2+

• 3+

• 1+

During the mechanism of methylmalonyl CoA mutase, what is the first step?

• Formation of a radical

• Hydrogen abstraction

• Formation of a covalent bond

• Release of a phosphate group

What is the role of cobalt in the methylmalonyl CoA mutase mechanism?

• It acts as a reducing agent.

• It provides structural support.

• It is a substrate.

• It is a product.

What happens to succinyl CoA after it is formed in the methylmalonyl CoA mutase cycle?

• It enters the TCA cycle.

• It is converted back to propionyl CoA.

• It is excreted from the cell.

• It enters the glycolysis pathway.

How many enzymes in humans use vitamin B12 for metabolic reactions?

• One

• Two

• Four

• Three