Oxidation of Alcohols Catalyzed by the Oxygen-Evolving Complex

The effects of alcohols on photosystem II reaction center complex preparations were examined. the order of effectiveness of alcohols to inhibit photosynthetic 0₂evolution was propargyl alcohol > glycerol > ethanol ≫ ethylene glycol. Inhibition by alcohols of H₂O₂-dependent 0₂evolution catalyzedby the oxygen-evolving complex (OEC) had the same concentration dependence as observed for the inhibition of photosynthetic 0₂evolution with the exception of glycerol, which inhibited H₂0₂-dependent 0₂evolution most effectively. Glycerol and propargyl alcohol were competitive inhibitors of H₂0₂-dependent 0₂evolution with inhibition constants of 12.9 mM and 1.16 M, respectively. Low concentrations of alcohols (<200 mM) in the presence of H₂0₂inhibited the OEC without causing the release of manganese. However, inactivation and loss of manganese can occur at higher concentrations of alcohol. the oxygen-evolving complex, in the presence of H₂0₂, catalyzes the oxidation of ethanol, glycerol, and propargyl alcohol to the respective aldehydes. A mechanism for this alcohol oxidase reaction catalyzed by the OEC is proposed.