<unk>  is a class of enzyme, specifically NAD-dependent histone deacetylases (class 3), found in both prokaryotes and eukaryotes.  They have been known to affect cellular metabolism through selective gene expression in eukaryotes (plants and animals).  The name comes from silent mating type information regulation two, the gene responsible for cellular regulation in yeast.
Sirtuin
Caspase
Cycasin
Ramogen
Pegaspargase
Ubiquinol oxidase
Brinase
Triptans