It is worth mentioning that
SIRT4 has no obvious deacetylation activity and the deacetylation activity of SIRT6 is stronger than its deacetylase activity [3].
SIRT1, SIRT6, and SIRT7 are found in the nucleus; SIRT3,
SIRT4, and SIRT5 are found in the mitochondria; and SIRT2 is primarily found in the cytoplasm (21).
In humans, 18 HDACs have been discovered and they are classed into four main families: class I (HDACs 1, 2, 3, and 8), class II (HDACs 4, 5, 6, 7, 9, and 10), class III (SIRT1, SIRT2, SIRT3,
SIRT4, SIRT5, SIRT6, and SIRT7), and class IV (HDAC11) [20].
The HDACs are grouped into four classes: class I (HDACs 1,2, 3, and 8), class II (HDACs 4,5, 6,7,9, and 10), class III (SIRT1, SIRT2, SIRT3,
SIRT4, SIRT5, SIRT6, and SIRT7), and class IV (HDAC11) [74, 75].
Sirtum-4 (
SIRT4) is downregulated and associated with some clinicopathological features in gastric adenocarcinoma.
SIRT4 and SIRT6 function as mono-ADP-ribosyltransferases, which transfer the ADP-ribosyl moiety to the substrate protein including glutamate dehydrogenase 1, poly (ADP-ribose) polymerase 1 respectively.
The mitochondria contain three of the seven mammalian sirtuins, including SIRT3 and
SIRT4. (21) Mitochondrial sirtuins may enhance longevity through mimicking caloric restriction, which protects against age-related disease and dysfunction, including cancer initiation.
Xu, "Calorie restriction on insulin resistance and expression of SIRT1 and
SIRT4 in rats.," Biochemistry and Cell Biology, vol.