Cell extracts of Methanosarcina barkeri converted coenzyme F420 in an ATP-dependent reaction to the adenylylated derivative factor 390. Although it was reported previously (L. M. Gloss and R. P. Hausinger, BioFactors 1:237-240, 1988) that whole cells were unable to perform this conversion, we observed the conversion in 7 of 11 extracts, all of which were prepared from different batches of cells.