Adenosylcobalamin is formed inside the mitochondrium (the energy producing apparatus within the cell) when adenosine is transferred from ATP (the molecule that carries energy) to vitamin B12. This form of B12 is an essential cofactor to the enzyme that converts methylmalonyl-CoA to succinyl-CoA which is needed for energy production in the Kreb's cycle.
The MMA Test Teaches a Lot About Why B12 is So Important for Energy
First Study to Find a Link
The Discovery That Launched the Search for Treatment