Suicide inhibition as a likely cause of variable specific activity in trimethylamine dehydrogenase from bacterium W3A1.

Trimethylamine hydrogenase isolated from bacterium W3A1 grown on dimethylamine was of variable, but low specific activity and had modified spectral properties. Chemical analyses for Fe, S and P indicated that the [4Fe-4S] clusters of the modified enzyme are intact and that the covalently bound flavin is probably present, but in modified form. A peptide with absorbance maximum at 358 nm and fluorescence excitation and emission maxima in dimethylformamide at 358 nm and 495 nm, respectively, was isolated by gel chromatography and HPLC of tryptic peptides of acetamidylated, modified trimethylamine dehydrogenase. These spectral properties are similar to those of 4a- or 5a-substituted flavins and suggest that the enzyme had been modified by in vivo reaction with a suicide inhibitor. This inhibitor, or a compound giving rise to it, seems to be present in a commercial source of dimethylamine.