Table 2.

Classification and functions of histone deacetylase enzymes

HDAC classification	Subtypes	Location	Function/role
Class I	HDAC1, HDAC2, HDAC3, HDAC8	Nucleus	Participate in the regulation of histone deacetylation modification
Class II	IIAHDACs (HDAC4, HDAC5, HDAC7, HDAC9)	Shuttle between cytoplasm and nucleus	In response to mitogenic signals [165]
	IIb-HDACs (HDAC6 HDAC10)	Cytoplasm	HDAC6 is reported to modulate the function of the non-histone protein HSP90 [166]
Class III [167]	Seven members of this family are SIRT1 through SIRT7	SIRTs are located in cellular compartments: nucleus, cytoplasm, and mitochondrion	Involved in cell ageing and energy metabolism processes [168–170]
Class IV	HDAC11	nucleus	Implicate in the regulation of interleukin-10 expression [171, 172]