Related Experiment Video
Updated: Sep 22, 2025

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
Published on: November 22, 2014
Human B12-dependent enzymes: Methionine synthase and Methylmalonyl-CoA mutase
Romila Mascarenhas1, Harsha Gouda1, Markus Ruetz1
1Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States.
Abstract:
Humans have only two known cobalamin or B12-dependent enzymes: cytoplasmic methionine synthase and mitochondrial methylmalonyl-CoA mutase. A complex intracellular B12 trafficking pathway, comprising a multitude of chaperones, process and deliver cobalamin to the two target enzymes. Methionine synthase catalyzes the transfer of a methyl group from N5-methytetrahydrofolate to homocysteine, generating tetrahydrofolate and methionine. Cobalamin serves as an intermediate methyl group carrier and cycles between methylcobalamin and cob(I)alamin. Methylmalonyl-CoA mutase uses the 5'-deoxyadenosylcobalamin form of the cofactor and catalyzes the 1,2 rearrangement of methylmalonyl-CoA to succinyl-CoA. Two chaperones, CblA (or MMAA) and CblB (or MMAB, also known as adenosyltransferase), serve the mutase and ensure that the fidelity of the cofactor loading and unloading processes is maintained. This chapter focuses on assays for purifying and measuring the activities of methionine synthase and methylmalonyl-CoA mutase.
More Related Videos
Related Concept Videos
Phase II Reactions: Methylation Reactions
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
Sulfur Assimilation
Electron Transport Chain: Complex I and II
ROS generation is regulated and maintained at moderate levels necessary...
Cofactors and Coenzymes
Cofactors can be metallic ions or organic molecules called coenzymes. These types of helper...
ATP Synthase: Mechanism
RNA Editing

