Human Tissue Kallikreins as Promiscuous Modulators of Homeostatic Skin Barrier Functions

The document discussed the role of human tissue kallikreins (KLKs), a family of serine protease endopeptidases, in skin barrier functions. These enzymes, found in the upper layers of the skin and associated structures like hair follicles and sweat glands, were initially thought to be limited to KLK5 and KLK7. However, research revealed that KLKs have broader roles, acting as mediators in skin desquamation, antimicrobial defense, and lipid permeability. They were also implicated in skin inflammation, pigmentation, and tumor suppression through proteinase-activated receptor signaling pathways. The review summarized the understanding of KLKs in skin physiology and pathobiology at the time.