Transglutaminases have a range of catalytic activities, most of which concern the post-translational modification of proteins. The most important of these activities is the cross-linking of proteins into large supramolecular networks. The widespread use of transglutaminases has increased the demand for an inexpensive, efficient and safe source of recombinant enzyme. We explored the use of plant-based systems for the production of this important industrial enzyme. Transgenic rice plants engineered with a rat prostate transglutaminase (rTG _p ), driven by the strong constitutive maize-1 ubiquitin promoter and its first intron, were shown to express the recombinant enzyme at the mRNA and protein levels. The Ca²⁺ dependence of the recombinant enzyme was confirmed by the biotin-labelled cadaverine-incorporation assay. In this communication we report the molecular and biochemical characterisation of transgenic plants expressing rTG _p and this sets the stage for establishing a bioreactor system for the production of transglutaminases in plants.