THE MECHANISM OF INHIBITION BY EDTA AND EGTA OF METHANOL OXIDATION BY METHYLOTROPHIC BACTERIA

Ethyleneglycol (aminoethylether) tetra-acetic acid (EGTA) was shown to be a potent competitive inhibitor of electron transfer between methanol dehydrogenase (MDH) and its electron acceptor cytochrome c(L). Addition of Ca2+ ions relieved the inhibition by removal of the inhibitory EGTA. Removal of EGTA by gel filtration completely relieved the inhibition. EGTA did not remove the tightly bound Ca2+ present in the MDH. Indo-1, a fluorescent analogue of EGTA, bound tightly to MDH in a 1:1 ratio but not to cytochrome c(L); binding was prevented by EGTA. It was concluded that EGTA inhibits methanol oxidation by binding to lysyl or arginyl residues on MDH thus preventing docking with cytochrome c(L).