Table 1. Characteristics of mammalian sirtuins.

Sirtuin	Classification	Molecular mass (kDa)	Catalytic activity	Localization
SIRT1	Class Ia	120	Deacetylase	Nucleus and cytoplasm
SIRT2	Class Ib	43	Deacetylase	Cytoplasm and nucleus
SIRT3	Class Ib	28/44	Deacetylase	Mitochondria, nucleus and cytoplasm
SIRT4	Class II	35	ADP-ribosyl transferase	Mitochondria
SIRT5	Class III	34	Deacetylase	Mitochondria
SIRT6	Class IVa	37	Deacetylase and ADP-ribosyl transferase	Nucleus
SIRT7	Class IVb	45	Deacetylase	Nucleus