Transglutaminases (TGs) are Ca2+ and thiol-dependent enzymes that catalyze posttranslational modifications of proteins. These covalent reactions include formation of isopeptide linkages between the carboxamide groups of protein-bound glutamine residues and ε-amino groups of protein-bound lysine and polyamine residues, hydrolysis and esterification of glutamine residues. Family of TGs includes at least nine members: TG 1-7, coagulation factor XIIIa, and the keratinocyte membrane bound TG form. TG has attracted considerable interest as a potential drug target. Its activity is thought to contribute to Alzheimer disease, Parkinson disease, Huntington disease, and supranuclear palsy. SensoLyte® Transglutaminase Activity Assay Kit provides a convenient assay for the high throughput screening of TG modulators and inhibitors. TG catalyzes covalent bond formation between a free amine group of poly-D-lysine, which is coated on the plate surface, and γ-carboxamide group of glutamine in biotin-TVQQEL peptide substrate. The reaction immobilizes biotin-conjugated peptide to the plate surface. The amount of immobilized biotin is determined using streptavidin-horseradish peroxidase (HRP) andTMB substrate. Colorimetric signal generated by HRP and TMB substrate is proportional to the activity of TG in a sample. Assay is performed in a convenient 96-well microplate format.