| Cobalamin (Vitamin B12) absorption |
| Transfer of cobalamin to the portal blood |
| Intracellular processing of cobalamin (reduction) |
| Mutation-caused epigenetic silencing of MMACHC |
| Regulation of MMACHC expression |
| Mitochondrial adenocylation of cobalamin and loading onto MMUT |
| Cobalamin loading and activation of MTR |