Studies on transglutaminases regulating cell fates and tissue formation.

Transglutaminase is an enzyme that catalyzes the cross-linking reaction of proteins via glutamine- and lysine residues. In mammals, eight isozymes are distributed in various tissues and play distinct roles by modifying their preferred substrate proteins. In these reactions, each isozyme specifically recognizes glutamine-residues. To clarify the primary sequences preferentially recognized by each enzyme, a phage-displayed peptide library was used to screen for preferred substrate sequences, resulting in the successful identification of 12-mer peptide sequences as the minimum substrate for each isozyme. Using these peptides, several applications were developed, including the detection of in situ and in vitro activities as well as the identification of substrates. For biological studies using these peptides, the induction of enzymatic activity during keratinocyte differentiation was investigated in a three-dimensional reconstructed culture system of epidermis. Additionally, to further clarify their physiological functions, model fish in which TGase genes were genetically deleted were established and characterized.