We have been interested in a family of enzymes named histone deacetylase (HDAC), which catalyzes the deacetylation of the acetyl lysine residue on histone tails. There are 18 members of human HDAC which can be divided into four classes. Class I, II and IV HDACs require zinc metal whereas Class III HDACs, which are named sirtuins, are NAD-dependent. Counteracting histone acetyltransferase (HAT), HDAC controls the histone acetylation level, structural modification of chromatin, and subsequent regulation of genes that are implicated in cell growth, proliferation, and differentiation. Furthermore, many non-histone proteins have been identified as HDAC substrates. Numerous studies have demonstrated that inhibitions of HDAC offer therapeutic benefits.