LSD1 the first known lysine-specific histone demethylase, is an 866 amino acid nuclear protein belonging to flavin monoamine oxidase family. It contains a SWIRM domain, a FAD-binding motif and an amine oxidase domain. This protein is ubiquitously expressed and is a component of several histone deacetylase complexes. LSD1 acts as a component of the CoREST and other transcriptional co-repressor complexes and also plays an important role in silencing neuronal-specific genes in non-neuronal cells. It is also known to demethylate Lys4 of histone H3, a specific tag for epigenetic transcriptional activation. Reports sμggest that that LSD1 plays an important role in stimulating androgen-receptor-dependent transcription converting oxygen to hydrogen peroxide (might use alternative electron acceptors). Along with nuclear FHL2, LSD1 serves as a novel biomarker predictive for prostate cancer.