Corrin/B12 Biochemistry: Methionine Synthase Reductase

The video explains the reaction mechanism of methionine synthase, an enzyme that uses vitamin B12. It details how cobalt acts as a super nucleophile, transferring electrons to facilitate methyl group transfer. The video also covers the methionine synthase reductase mechanism, highlighting electron flow from NADPH to FAD and FMN, ultimately reducing cobalt back to its active state.

What is the primary role of methionine synthase in humans?

• To oxidize cobalt

• To transfer a methyl group to cobalt

• To break down methionine

• To synthesize vitamin B12

Why is cobalt referred to as a 'super nucleophile' in the context of methionine synthase?

• Because it strongly attracts and transfers electrons to the methyl group

• Because it can transfer electrons to oxygen

• Because it has a low reduction potential

• Because it forms weak bonds with carbon

What type of bond is formed between cobalt and the methyl group in methionine synthase?

• Ionic bond

• Covalent bond

• Coordinate covalent bond

• Hydrogen bond

What happens to cobalt in methionine synthase when it interacts with molecular oxygen?

• It forms a covalent bond with oxygen

• It gets oxidized to a two plus state

• It gets reduced to a one plus state

• It becomes inactive

What is the function of methionine synthase reductase?

• To transfer electrons to oxygen

• To synthesize NADPH

• To reduce cobalt back to its active state

• To oxidize methionine

Which molecule donates electrons to FAD in the electron transfer process of methionine synthase reductase?

• Methionine

• Oxygen

• FMN

• NADPH

What is the role of FMN in the electron transfer mechanism of methionine synthase reductase?

• To reduce cobalt by transferring electrons

• To synthesize FAD

• To oxidize NADPH

• To transfer electrons to methionine

What is the process called when cobalt accepts a methyl group from adenosyl methionine?

• Oxidative methylation

• Reductive methylation

• Hydrolysis

• Phosphorylation

What role does histidine play in the active site of methionine synthase?

• It transfers electrons to FMN

• It oxidizes cobalt

• It deprotonates the thiol of homocysteine

• It binds to adenosyl methionine

What is regenerated at the end of the methionine synthase mechanism?

• Histidine in its resting state

• NADPH

• Adenosyl methionine

• Cobalt in the two plus state