Cofactor substitution

A number of photochemical approaches for cofactor substitution or regeneration to achieve ferrous heme reduction and support P450 catalysis have been reported. The main principle behind is the use of artificial photosensitive compounds, which mimic the function of photosynthetic or-... 

Cofactor Substitution, Mediated Electron Transfer to Enzymes... 

Examples of enzymatic and electrochemical cofactor regeneration as well as chemical and electrochemical cofactor-substitution systems are depicted in Fig. 1. Cofactor regeneration replaces the metabolic cofactor regeneration fotmd in vivo, while cofactor substitution shortcuts the natural system and transfers electrons via the mediator directly to the oxidoreductase or possibly another protein in the electron-transfer chain. The natural monooxygenase system depicted here consists of three proteins, typical for several bacterial P450s, but systems with two or only one component also exist and the principles for the cofactor regeneration and substitution are the same. 

Cofactor Substitution, Mediated Electron Transfer to Enzymes, Fig. 1 Examples of artificial cofactor regeneration and cofactor substitution used in in vitro enzyme catalysis. Cofaclor regeneration (middle) replaces the metabolic cofaclor regeneration found in vivo (top), while cofactor substitution (bottom) shortcuts the natural system and... 

Cofactor Substitution, Mediated Electron Transfer to Enzymes, Fig. 2 Examples of the structure and redox potential (vs. SHE) of several mediators used for electron transfer between electrodes and enzymes. The mediators with positive redox potential were used in... 

The enzyme can use dATP but no other nucleotides as a cofactor substitute. The dATP (66 ixM) results in a 60% decrease in ligation activity and is a competitive inhibitor against ATP with a Kj of 35 (jlM (4). NAD cannot serve as a cofactor. 

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