The byproduct of an enzyme reaction once though unimportant plays a direct role in a particular worm\'s aging process, a Swiss-led team of researchers said. The findings suggest a key aspect of sirtuin enzyme activity may have been overlooked and point to new mechanisms for possibly extending lifespan, researcher Michael Ristow of ETH Zurich Switzerland said in a paper published Monday in Nature Chemical Biology. Sirtuin enzymes are involved in modifying histones, protein complexes that allow packing and storage of DNA, the research team led by Ristow said. In many organisms, sirtuins have been linked to regulating DNA health and, by extension, longevity, but it was unclear how these enzymes, and the modifications they make, are linked directly to longevity. Ristow and his colleagues demonstrated that the conversion of nicotinamide adenine dinucleotide to nicotinamide during the course of the sirtuin reaction had an unexpectedly strong impact on increasing lifespan in the free-living, transparent nematode. The authors said sirtuins are expendable if nicotinamide or a subsequent product are added directly to cells or the worm they studied.