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).