L-Lysine is believed to prevent osteoporosis of bones, which is a characteristics of vascular calcification. Glutaric aciduria type I and pyridoxine-dependent epilepsy occurs due to lack of L-lysine catabolic pathway. Lysine participates in the regulation of NO (nitric oxide) synthesis. It possesses antiviral activity, therefore it is used in the treatment of Herpes simplex. L-Lysine is associated with a number of biochemical reactions such as acetylation, O-linked glycosylation, ubiquitination and protein methylation. Poly-L-lysine is considered as a biocompatible polymer and serves for the purpose of drug delivery across cell membrane. It is useful as one of the nanosized contrast agents in MRI (magnetic resonance imaging).