Glutathione is such a critical soldier in our line of defense that our bodies make it themselves. We even have mechanisms that recycle and reuse it. But what happens when our toxic Defy GHK Cu (glycyl L histidyl L lysine) is a naturally occurring copper binding peptide found in human plasma. As levels decline with age, so may its support of the biological processes involved in collagen production, skin Glutathione: An Incredible Ingredient for Skin Rejuvenation Titan Biotech Ltd. What Is Glutathione & Its Uses