Micromolar amounts of superoxide dismutase (SOD) or parabenzoquinone (PBQ) inhibit the membrane-bound myoinositol dehydrogenase of Bacillus pumilus strain 5 in the mode of this enzyme transferring electrons to 2,6-dichlorophenol indophenol (DCPIP). The inhibition trends are similar to those reported earlier by us for the inhibition by mannitol and benzoate. We postulate that the transfer of electrons from the enzyme to DCPIP involves in its rate-limiting step, a catalytic intermediate in the nature of superoxide (O2-) and/or hydroyl free radical (OH.). Scavenging of any one or both of these radicals, therefore, inhibits the electron transfer reaction. PBQ serves as an electron sink in the reaction preventing the reduction of DCPIP.
Free radical research communications 02/1987; 4(2):105-8. DOI:10.3109/10715768709088094