Enzymatic oxidation of tetramethyl-p-phenylenediamine and p-phenylenediamine by the electron transport particulate fraction of Azotobacter vinelandii.

The ability of the electron transport particulate fraction of Azotobacter vinelandii strain O to oxidize tetramethyl-p-phenylenediamine (TMPD) and p-phenylenediamine (PPD) was examined in detail. The highest specific activity for TMPD and PPD oxidation concentrated in the A. vinelandii O R(3) fraction. The A. vinelandii O R(3) fraction was used to develop a standard manometric assay which gave optimal oxidation rates for both of these dyes. The conditions of the assay and all essential related enzymatic kinetic parameters are presented. Other para derivatives of phenylenediamines also were oxidized readily, whereas ortho and meta derivatives were not. Hydroquinone, p-hydroxybenzoic acid, p-cresol, tyrosine, pyrogallol, pyrocatechol, and diphenylamine were not able to serve as electron donors for the A. vinelandii O R(3) system. The probable involvement of a particle-bound cytochrome oxidase is indicated by the marked sensitivity of both TMPD and PPD oxidation to cyanide, axide, phenylhydrazine, hydroxylamine, and, to a lesser degree, carbon monoxide.