(2R,3R,5S,6R)-6-(methyl)-2-(S-pantetheinyl)-carbapenam-3-carboxylate + methylcob(III)alamin + S-adenosyl-L-methionine = (2R,3R,5S,6R)-6-(ethyl)-2-(S-pantetheinyl)-carbapenam-3-carboxylate + cob(III)alamin + 5'-deoxyadenosine + L-methionine — reaction