KDM1, also known as Lysine-specific histone demethylase 1A, is an enzyme that plays a crucial role in the regulation of gene expression. It is involved in the process of demethylation, which is the removal of methyl groups from lysine residues on histone proteins. This modification of histones can lead to changes in the accessibility of DNA to the transcription machinery, thereby affecting whether a gene is turned on or off.