Figure 16. The chemical structures of (A) DPI and (B) FMN are compared. It has been proposed that the effects of DPI are mediated through the general inhibition of flavo-enzymes, such as mitochondrial Complex I (NADH dehydrogenase), via the targeting of FMN. The three known flavin-containing protein components of Complex I are: NDUFV1 (51 kD), NDUFV2 (24 kD) and NDUFV3 (10 kD). It has been suggested that DPI chemically reacts with FMN, interrupting its function and impairing electron transport. In the human genome, there are ~90 flavo-proteins; more than two-thirds require FAD, while only ~15% require FMN. Flavo-proteins are very often localized to the mitochondria, because of their role in redox reactions. Nearly all flavo-proteins (~90%) catalyze some form of redox reaction.