Though the exact role of MMACHC is unknown， its C-terminal region shows similarity to TonB， which is a bacterial protein involved in energy transduction for cobalamin （vitamin B12） uptake. Therefore， it is suggested that MMACHC may have a role in the binding and intracellular trafficking of cobalamin. MMACHC mutations are linked with methylmalonic aciduria and homocystinuria type cblC. MMACHC is widely expressed， it is expressed at higher level in the fetal liver， however it is also expressed in the spleen， lymph node， thymus and bone marrow. MMACHC is weakly or not expressed in the peripheral blood leukocytes.
