chain amino acid transaminase B (IlvE) [3], and aspartate aminotransferase [8], but it may also modify other (as yet unknown) physiological targets [2; 3; 4; 9]. Enamines tautomerize to imines, very reactive and labile compounds as well [10], which hydrolyze to the corresponding keto acids and ammonia at a relatively slow rate (half-life of the imine derived from L-Leu oxidation: 6 s at pH 7.7 and 21 s at pH 8.7 [11]; 4 min for the threonine-derived enamine intermediates at pH 9.7 and 25 \({}^{\circ}\)C [12], and 1.5 s for the 2-aminoacrylate/iminopyruvate intermediate generated by tryptophanase at pH 8.0 and 30 \({}^{\circ}\)C [13], as quoted in [1]). The complex phenotypes generated by ablation of RidA genes demonstrate the importance of the protein products in buffering 2 AA stress [9; 14; 15; 16]. It is remarkable that in some bacteria species lacking RidA, even motility is defective, whereas plants that are lacking RidA activity exhibit reduced root growth [14; 17]. The selective pressure imposed by the need to prevent metabolic damage by reactive enamines/imines may explain the conservation of Rid activity from early evolution [6]. In vitro assays have shown how some members of the YigF/YER057c/UK114 protein family accelerate the hydrolysis of the enamine/imine that is generated by Ser/Thr dehydatase from serine, Cys desulfhydrase from cysteine and the imine released from L-amino acid oxidases and different amino acids [1; 6; 15]. After these discoveries, the YigF/YER057c/UK114 protein family was renamed Rid (Reactive intermediate deaminase) family [6]. The Rid family currently comprises eight subfamilies, RidA and Rid1 to Rid7 [6]. The RidA subfamily includes members from Eukaryotes and Archaea, and is also widely distributed among Eubacteria species, with the best characterized member being RidA from _S. enterica_[4]. The other seven subfamilies (Rid1 to Rid7) are unique to prokaryotes. Interestingly, some bacteria may contain up to 11 different Rid proteins. Specific signature patterns identify each subfamily [6]. Several crystal structures of RidA proteins have been determined long before the discovery of their enzymatic activity [18; 19; 20]. RidA proteins are homotrimers with the cleft between two adjacent monomers harbouring the active site. Figure 1: Proposed detoxifying function of the Reactive intermediate deaminase (Rid) proteins. The figure summarizes the reactions catalyzed by the indicated pyridoxal phosphate (PLP)-dependent enzymes leading to the formation of the toxic compound 2-aminoacrylate (2 AA) that tautomerizes to 2-iminopropionate (iminopyruvate), which is hydrolyzed to pyruvate and ammonia non-enzymatically following formation of a 2-carbonalamine intermediate (_left branch_, dashed arrows ) or by a RidA protein (_right branch_). The archetype of the eukaryotic RidA family, and the first mammalian member to be identified, was UK114 originally detected as a component of a perchloric acid-soluble extract from _Capra hircus_ (goat) liver. Because of its immunomodulatory properties and its ability to elicit cytotoxic antibodies against some solid tumors, UK114 was described as a tumor-associated antigen [21; 22; 23; 24; 25; 26; 27; 28; 29; 30]. The human homolog of UK114 is encoded by a single gene, annotated as _HRSP12_, localized on chromosome 8 and organized in six exons ([[http://genome.ucsc.edu/](http://genome.ucsc.edu/)]([http://genome.ucsc.edu/](http://genome.ucsc.edu/))). Previous studies and RNA Seq analyses revealed that--in the adult--the expression of _HRSP12_ is high in hepatocytes, lower in renal distal tubular epithelial cell and weak in all of the other tissues. Moreover, _HRSP12_ is up-regulated during differentiation and in proliferating cells, while it is down-regulated in tumors [31; 32]. Contrasting results concern the intracellular localization of RidA proteins in eukaryotes. Yeast genomes contain two paralogs encoding RidA proteins.