QUINOPROTEIN ALCOHOL-DEHYDROGENASE OF ACETIC-ACID BACTERIA - KINETIC-STUDY ON THE ENZYME PURIFIED FROM ACETOBACTER-METHANOLICUS

An alcohol dehydrogenase (ADH) complex consisting of subunits I, II, a nd III and the free subunit II were purified from Acetobacter methanol icus. The kinetic parameters of the purified ADH were investigated wit h several artificial electron accepters, Simultaneous reactions with d ifferent electron accepters showed that these electron accepters compe ted with each other, Although free subunit II did not show any enzyme activity, part of the activity was restored after reconstitution with subunit I/III complex purified from Gluconobacter suboxydans, 2-n-Hept yl-4-hydroxyquinoline-N-oxide (HQNO) non-competitively inhibited all t he reductase activities of native ADH, while the ferricyanide reductas e activity of hybrid ADH was not inhibited by HQNO but the ubiquinone reductase activity was inhibited competitively, The kinetic study of n ative and hybrid ADHs suggests that at least three heme c moieties are involved in the reduction of ferricyanide and that the reduction of u biquinone occurs in subunit II at a site different from the ferricyani de reacting site.