Adenosylhomocysteinase (SAHase or AHCY) is an enzyme responsible for catalyzing the hydrolysis of S-adenosylhomocysteine (SAH) into adenosine and homocysteine, a crucial step in the methylation process. It consists of multiple functional domains and is primarily located in the cytoplasm. SAHase plays a crucial role in regulating methylation reactions and homocysteine metabolism, affecting DNA methylation, post-translational protein modifications, and signaling pathways. The expression of SAHase is tissue-specific, and mutations or dysregulation in its gene are associated with various diseases, including cardiovascular diseases, neurodegenerative diseases, and cancer. The activity of SAHase is regulated by various factors, influencing the cell's epigenetic state and function.