Keratyna

Keratyna is a family of fibrous structural proteins that form the intermediate filaments of epithelial cells. They are highly insoluble and resistant to proteolysis, which supports the mechanical integrity of tissues such as skin, hair, and nails. Keratins are encoded by a large gene family, mainly KRT genes. In vertebrates, keratins are classified into type I (acidic) and type II (basic to neutral) keratins. They function as obligate heterodimers of one type I and one type II keratin that assemble into robust intermediate filaments.

Most keratins are expressed in epithelial tissues; hair, nails, horns, and beaks contain hard keratins, which have higher cysteine content and form extensive disulfide cross-links, contributing to rigidity. Soft keratins are found in the epidermis and other stratified epithelia.

Keratinocytes undergo a process called keratinization or cornification as they move toward the surface. They mature, lose their nucleus and organelles, and accumulate keratin filaments and cross-links to form the stratum corneum, the outer protective layer.

Genetic mutations in keratin genes can disrupt filament assembly and cause keratinopathies, such as epidermolysis bullosa simplex and various hair fragility disorders, highlighting the structural role of keratins.

Keratin-derived materials are used in cosmetics and research, including keratin-based hydrogels and peptide fragments. However, the effectiveness of keratin treatments for hair depends on formulation and chemical modification, and keratin cannot readily replace native keratin in tissues.