Any of a family of proteins that characteristically bind NAD and enzymatically remove acetyl groups from a range of targets, notably histones, transcription factors, and other enzymes. This deacetylase activity is thought to play a significant role in the post-transcriptional modification of proteins. Evidence suggests that sirtuins play numerous roles in cells, including stress responses, DNA repair, energy metabolism, ageing, and tumour formation. Controversy surrounds the proposition that sirtuins mediate the health benefits of calorie-restricted diets, such as increased longevity, and that sirtuins are activated by the compound resveratrol, found in red wine.