Isolation of substrates of epidermal transglutaminase from bovine epidermis

Substrates of the transglutaminase specific to epidermis were identified by fluorescent labeling of bovine epidermal homogenates with dansyl cadaverine. This lysine analog was preferentially incorporated into a soluble protein of 150,000 MW. A highly insoluble protein was also labeled; this protein was solubilized and extracted following chemical cleavage with cyanogen bromide. The soluble and insoluble substrates of epidermal transglutaminase were immunochemically related, as shown by precipitation in agar or by chromatography on antibody affinity columns. They were distinguished from the fibrous, α-helical and sulfur-rich matrix proteins of skin as well as from fibrinogen and cold insoluble globulin of plasma.