When Heinrich B. Waelsch [53,13], Laszlo Lorand [33] and John E. Folk [20]-the latter who passed away on Dec 27th 2010 and to whom we wish to dedicate the present Editorial -began to investigate at the middle of the past century on the calcium dependent transamidating activities contained in the guinea pig liver and blood, no one could imagine that transglutaminase (TG, EC 2.3.2.13) would become at the beginning of the new millennium one of the most interesting biocatalyst for industrial applications in several different fields. An accurate historical overview of the first 50 years of TG research was recently reported by Beninati et al. [3] in occasion of the "IX Conference on Transglutaminase and Protein Crosslinking" held in Marrakesh in the early days of September 2007.The complete name of the enzyme, R-glutaminyl-peptide:amineg-glutamyltransferase, indicates that the catalysis consists of the acyl transfer of g-glutamyl residues, present in protein or peptide substrates (acyl donor), to an acyl acceptor substrate, resulting in a variety of different products depending on the involved molecules [21]. The transamidation reaction occurs when the acyl acceptor is either the ε-amino group of an endoprotein lysine residue or a low molecular mass primary amine, generating ε-(g-glutamyl)lysine crosslinked linear or branched homo-and heteropolymers, in the first case, or protein-amino derivatives in the latter. The wide range of interest on TG biological role is mostly related to the existence of multiple molecular forms of the enzyme which are present in different organisms, such as bacteria, plants, Although TG was mostly studied for the ability to post-translationally remodel many different proteins in vivo, its reaction has attracted the attention of many scientists in the last twenty years as an effective way to manipulate the structure of proteins of different origin outside the living cells. Therefore, applied investigations with the different enzyme isoforms have been carried out in different fields, from biomedicine and cosmetics to food, leather, and textile industry [41]. As far as the human health applications, concentrated Factor XIII, a zymogenic form of the enzyme, is used as therapeutic agent to correct blood coagulation in a rare genetic condition due to its deficiency and to reduce bleeding risks [36]. Factor XIII was the first TG isoform used to modify protein and peptide substrates in vitro [45]. In addition, the so-called "tissue" TG (type 2) is an effective biomedical technological tool exploited for the diagnosis of an autoimmune pathology like the celiac disease [15,19]. Also this isoform was extensively tested to modify both structure and biological properties of several polypeptides in vitro [41]. However, both Factor XIII and type 2 TG are not really attractive for industrial uses, since their production is expensive and they cannot be easily manipulated outside of their natural environment. Moreover, further molecular forms of the enzyme extracted from plant or animal tissues were never s...