Cobalamin-dependent enzyme or transport protein

The term "B12-dependent enzymes and transport proteins" refers to a heterogeneous group of enzymes and transporters that require vitamin B12 (cobalamin) as an essential cofactor or ligand for their function. Prominent examples among enzymes include methionine synthase and methylmalonyl-CoA mutase, which are critical for amino acid and fatty acid metabolism in humans[4][6][5]. Transport proteins such as haptocorrin, intrinsic factor, and transcobalamin mediate gastrointestinal absorption, plasma distribution, and tissue uptake of B12[3][2][5]. In bacteria and mammals, additional membrane-bound and cytoplasmic transporters, such as ATP-binding cassette transporter family members (ABCD4) and their adaptors (e.g., LMBD1), are crucial for intracellular cobalamin trafficking[2][1]. Dysfunction of individual B12-dependent enzymes or transport proteins underlies a range of human diseases, notably megaloblastic anemia, various inherited metabolic disorders, and neurological syndromes[2][5]. As a group, these proteins are essential for normal cell physiology but do not constitute a single molecular target, so use of the plural "B12-dependent enzymes and transport proteins" is over-broad and non-canonical; specific enzymes or transporters should be individually named for therapeutic or biomarker targeting[2][3][5].

Other names

Vitamin B12-dependent enzymeVitamin B12 transporterB12-dependent proteincobalamin-dependent protein

Supplementation replenishes B12 as an essential cofactor, restoring impaired enzymatic activity. Some investigational drugs exploit receptor-mediated endocytosis (e.g., transcobalamin-mediated uptake).