<p>The TIM-barrel fold is a closed barrel structure composed of an eight-fold repeat of beta-alpha units, where the eight parallel beta strands on the inside are covered by the eight alpha helices on the outside [<cite idref="PUB00027645"/>]. It is a widely distributed fold which has been found in many enzyme families that catalyse completely unrelated reactions [<cite idref="PUB00027646"/>]. The active site is always found at the C-terminal end of this domain.</p><p>Proteins in this entry are a variety of NADH:flavin oxidoreductase/NADH oxidase enzymes, found mostly in bacteria or fungi, that contain a TIM-barrel fold. They commonly use FMN/FAD as cofactor and include:<ul><li>dimethylamine dehydrogenase</li><li>trimethylamine dehydrogenase</li><li>12-oxophytodienoate reductase</li><li>NADPH dehydrogenase</li><li>NADH oxidase</li></ul></p>