N(6)-methyl-L-lysyl-[protein] + formaldehyde + AH2 => N(6),N(6)-dimethyl-L-lysyl-[protein] + A + H2O
n(6)-methyl-l-lysyl-[protein] + formaldehyde + ah2 => n(6),n(6)-dimethyl-l-lysyl-[protein] + a + h2o