Genetic disorders of vitamin B(12) 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.