Met-enkephalin is a naturally occurring peptide in the body, classified as an opioid peptide. It is composed of five amino acids and plays a crucial role in modulating pain, stress, and emotional responses. Met-enkephalin binds to opioid receptors in the brain, helping to reduce the perception of pain and promote feelings of well-being. This peptide is part of the larger family of endorphins, which are hormones produced by the pituitary gland. Met-enkephalin is particularly involved in the body's response to stress and can influence behaviors related to reward and addiction. Its functions highlight the complex interplay between neurochemicals and emotional health.