Converts cyanocobalamin (CN-B12) to adenosylcobalamin (AdoCbl), the inducer of the eut operon. Is not active on cobinamide nor other intermediates in the adenosylcobalamin synthetic pathway. Allows full induction of the eut operon. 2 ATP + 2 cob(II)inamide + 2 H2O + reduced [electron-transfer flavoprotein] = 2 adenosylcob(III)inamide + 2 diphosphate + 3 H(+) + oxidized [electron-transfer flavoprotein] + 2 phosphate ATP + cob(I)alamin-[corrinoid adenosyltransferase] = adenosylcob(III)alamin + apo-[corrinoid adenosyltransferase] + triphosphate Binds 1 divalent metal cation ion per homodimer with both subunits providing Cys ligands; Fe(2+) gives most activity and is possibly the physiological cofactor. Amine and polyamine degradation; ethanolamine degradation. Homodimer. Belongs to the Cob(I)alamin adenosyltransferase family. EutT subfamily. In strain MG1655 the eut operon is interrupted by the CPZ-55 prophage, encoding 9 genes situated between eutA and eutB, which are translated in the other direction. CPZ-55 may prevent expression of the eut operon in strain MG1655. Strain W3110 does not have this prophage element and should be able to express the operon.