Page - (000058) - in Biomedical Chemistry: Current Trends and Developments

Scheme 1.1.42: Mechanism of ethanol oxidation in cells. 1.1.5.5. FAD − a More Versatile Coenzyme Flavin adenine dinucleotide (FAD) (Fig. 1.1.10) is another coenzyme used in oxidation reactions and is normally associated tightly to a protein, usually designated as a flavoprotein. For example, in chorismate synthase, FAD is linked through the flavin ring C(2)=O to one protein histidine residue (His106) (Scheme 1.1.44). FAD is considered a more versatile coenzyme than NAD+, because it can participate in oxidation reactions by several different mechanisms. For example, oxidation of dihydrolipoate involves a nucleophilic attack on C-4a whereas oxidation of an amino acid involves a nucleophilic attack on the N-5 position (Scheme 1.1.43). Figure 1.1.10: Structure of flavin adenine dinucleotide (FAD).