Enzymatic Hydroxylations with Molecular Oxygen

Abstract For thermodynamic reasons, biological hydroxylations cannot usually proceed according to the β‐oxidation scheme, but are possible only with the aid of molecular oxygen by a route requiring a large amount of energy. The corresponding enzymes, known as “mixed function oxygenases” or more appropriately “monooxygenases”, require two reduction equivalents for the activation of oxygen. The cytochrome P‐450‐dependent monooxygenases are taken as examples for the discussion of the chemistry of the enzymatic catalysis. The central problem of the activation of oxygen has not yet been solved, but an “oxenoid” mechanism can be deduced from model investigations.