Genetic disorders of vitamin B12 metabolism: eight complementation groups - eight genes

Vitamin B-12 (cobalamin, Cbl) is an essential nutrient in human metabolism. Genetic diseases of vitamin B-12 utilisation constitute an important fraction of inherited newborn disease. Functionally, B-12 is the cofactor for methionine synthase and methylmalonyl CoA mutase. To function as a cofactor, B-12 must be metabolised through a complex pathway that modifies its structure and takes it through subcellular compartments of the cell. Through the study of inherited disorders of vitamin B-12 utilisation, the genes for eight complementation groups have been identified, leading to the determination of the general structure of vitamin B-12 processing and providing methods for carrier testing, prenatal diagnosis and approaches to treatment.