MMADHC and Methylmalonic aciduria: When cobalamin is released into the cytosol, the cytoplasmic chaperons methylmalonic aciduria and homocystinuria type C protein (CblC, gene MMACHC) and methylmalonic aciduria and homocystinuria type D protein (CblD, gene MMADHC) initiate processing of the incoming vitamin, which starts with its reduction to Co2+ accompanied by removal of the original exchangeable group [12].