3.1. Sirtuins
Sirtuins, also known as Sir2 proteins (silent information regulator 2), have a conserved catalytic core domain characterized by its requirement for nicotine adenine dinucleotide (NAD) to catalyze protein deacetylation by transferring the acetyl group from the lysine to NAD+, resulting in deacetylated lysine, nicotinamide (NAM) and 2′-O-acetyl-ADP- ribose (Figure 2B) (Blander & Guarente, 2004). These proteins are evolutionarily conserved within the three domains of bacteria, archaea, and eukaryotes. The sirtuins have a conserved catalytic core domain, characterized by its requirement for nicotine adenine dinucleotide (NAD), to catalyze deacetylation by transferring the acetyl group from the lysine to NAD+(Michan & Sinclair, 2007; Sauve et al., 2006).
Bacterial genomes and most archaea encode one or two sirtuins, except for Escherichia coli , which encodes three, whereas eukaryotes typically contain multiple sirtuins. Lammers (2021) suggests that the low number of sirtuins in bacteria allows them to control specific physiological processes where they can present a very narrow substrate range or may have a high degree of promiscuity in substrate recognition. An enzyme with high substrate promiscuity may also have specificity for certain substrates because they are processed more efficiently due to the region within the cell where the reaction occurs or by transcriptional regulation of their expression levels (Lammers, 2021).