Demethylase
Demethylases are enzymes that remove methyl (CH3-) groups from nucleic acids, proteins (in particular histones), and other molecules. Demethylase enzymes are important in epigenetic modification mechanisms. The demethylase proteins alter transcriptional regulation of the genome by controlling the methylation levels that occur on DNA and histones and, in turn, regulate the chromatin state at specific gene loci within organisms.
For many years histone methylation was thought to be irreversible, due to the fact that the half-life of the histone methylation was approximately equal to the half-life of histones themselves. In 2004, Shi et al. published their discovery of the histone demethylase LSD1 (later classified as KDM1A), a nuclear amine oxidase homolog. With the new found interest in epigenetics, many more families of histone demethylases have been found. Defined by their mechanisms, two main classes of histone demethylases exist: a flavin adenine dinucleotide (FAD)-dependent amine oxidase, and an Fe(II) and α-ketoglutarate-dependent dioxygenase, with the general proposed mechanisms shown in the figure below.
Histone demethylase proteins have a variety of domains that serve different functions. These functions include binding to the histone (or sometimes the DNA on the nucleosome), recognizing the correct methylated amino acid substrate and catalyzing the reaction, and binding cofactors. Cofactors include: alpha-keto glutarate (JmjC-domain containing demethylases), CoREST (LSD), FAD, Fe (II) or NOG (N-oxalylglycine). Domains include:
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