( ransferring an oxygen atom from the enz...)Scientists take 'snapshots' of enzyme action

First, the cofactor (known as NADPH) binds to a molecule known as FAD, which is a coenzyme attached to the FMO, and transfers a hydride ion to it. That makes the FAD group capable of accepting molecular oxygen. Then, when the substrate arrives, the cofactor leaves so that the substrate can bind to the same site on the FAD group. At this moment an oxygen atom from molecular oxygen is attached to the substrate, and the hydride ion obtained from the cofactor combines with the other oxygen atom to form a water molecule, which is released. Once the substrate is oxygenated, it leaves the enzyme and the cofactor binds again.

"With this back-and-forth, alternating binding, the process repeats over and over for continuous turnover of the product," Swaminathan says.

The details of this process may help scientists understand what happens in cases where compounds are not properly metabolized, and possibly develop corrective measures.

One example is a condition called trimethylaminuria, also known as "fish odor syndrome," which results from defective FMOs. Affected individuals are unable to oxygenate trimethylamine, a byproduct of protein digestion released by bacteria living in the gut. People with the disorder release trimethylamine through breath, sweat, and urine, producing a fish-like odor that can be embarrassing and result in psychological effects such as withdrawal and depression.

People with defective FMOs might also suffer additional side effects from drugs, industrial compounds, or other chemicals.