Corrin/B12 Biochemistry: Methionine Synthase Reductase

What is the primary role of methionine synthase in humans?

• To transfer a methyl group to cobalt

• To synthesize vitamin B12

• To oxidize cobalt

• To reduce molecular oxygen

Why is cobalt considered a super nucleophile in methionine synthase?

• Because it has a low reduction potential

• Because it can transfer electrons to oxygen

• Because it forms weak ionic bonds

• Because it strongly attracts methyl groups

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 reacts with molecular oxygen?

• It becomes inactive

• It forms a covalent bond with oxygen

• It is oxidized to a two plus state

• It is reduced to a one plus state

Which enzyme is responsible for reducing cobalt back to its active state in methionine synthase?

• Methionine synthase

• Methionine synthase reductase

• NADPH oxidase

• Cytochrome P-450

What is the role of NADPH in the methionine synthase reductase mechanism?

• To oxidize FAD

• To methylate homocysteine

• To transfer electrons to FMN

• To provide electrons for reducing cobalt

What is the result of the reductive methylation process in methionine synthase?

• Methylation of histidine

• Reduction of FMN

• Oxidation of cobalt

• Formation of adenosyl homocysteine

In the methionine synthase mechanism, what role does histidine play?

• It oxidizes cobalt

• It binds to the methyl group

• It transfers electrons to FMN

• It deprotonates homocysteine

What is the significance of maintaining cobalt in the one plus oxidation state in methionine synthase?

• It allows cobalt to act as a super nucleophile

• It prevents the formation of superoxide

• It enables the synthesis of vitamin B12

• It stabilizes the enzyme structure

What is the final product formed when homocysteine attacks the methyl group in methionine synthase?

• Histidine

• Cobalt oxide

• L-methionine

• Adenosyl methionine