Activation of α-keto acid-dependent dioxygenases: application of an {FeNO}7/{FeO2}8 methodology for characterizing the initial steps of O2 activation.

The α-keto acid-dependent dioxygenases are a major subgroup within the O(2)-activating mononuclear nonheme iron enzymes. For these enzymes, the resting ferrous, the substrate plus cofactor-bound ferrous, and the Fe(IV)═O states of the reaction have been well studied. The initial O(2)-binding and activation steps are experimentally inaccessible and thus are not well understood.

Reaction coordinate of isopenicillin N synthase: oxidase versus oxygenase activity.

Isopenicillin N synthase (IPNS) can have both oxidase and oxygenase activity depending on the substrate. For the native substrate, ACV, oxidase activity exists; however, for the substrate analogue ACOV, which lacks an amide nitrogen, IPNS exhibits oxygenase activity. The potential energy surfaces for the O-O bond elongation and cleavage were calculated for three different reactions: homolytic cleavage via traditional Fenton chemistry, heterolytic cleavage, and nucleophilic attack.