In particular, _Saccharomyces cerevisiae_ YE0057 cR/_HMF1_ codes for a cytosolic protein dispensable for viability, whereas its paralog, YIL051c/_MMF1_, encodes a mitochondrial matrix protein that is essential for isoleucine biosynthesis and mitochondria stability [33; 34], as further confirmed and clarified in a recently published work [35]. Rat and human homologs of UK114 were localized in the cytoplasm, in the peroxisal matrix, and, occasionally, in the nucleus of differentiating cells, whereas no evidence of import in the mitochondron was reported [31; 36]. Mammalian UK114 homologs are \(N\)-acetylated on the second amino acid (a serine residue) [21; 29]. Interest on UK114 has also been recently stimulated by the identification of Der f 34, which is a major allergen of house dust mite (_Dermatophagoides farinae_). This homolog of UK114 is endowed with RidA activity [37]. Der f 34 and a component of the spores of the fungus _A Aspergillus fumigatus_ cross-react with IgE from patients allergic to indoor allergens, suggesting that members of the RidA protein family may represent important pan-allergens that are conserved across different organisms [37]. Although enamine/imine hydrolase activity has been reported in some assays [2; 3; 33], to our knowledge, an in depth biochemical characterization of a mammalian RidA is still lacking. In contrast, several functions have been attributed to UK114: endoribonuclease activity, p14.5 inhibitor of protein synthesis, activator of the \(\mu\)-calpain protease. UK114 was also described as HRP12 (heat-responsive protein 12) involved in mRNA decay [38; 39; 40; 41]. These multiple activities, which may need independent confirmation, are difficult to reconcile with the current knowledge on the Rid family. However, it cannot be ruled out that different members could be endowed with similar activity, but function in different processes [4]. Studies on _S. enterica_ strains lacking RidA protein highlighted the interchangeable function of RidA proteins in preventing damage by 2 AA. The inhibition of _S. enterica_ IlvE by 2 AA that is generated by the threonine/serine dehydatases IlvA or TdcB, two PLP-dependent enzymes, was assessed both in vitro and in vivo [3]. In an in vitro reconstituted system, the human UK114, as well as other homologs from an archaeon and from plants, proved to be as proficient as _S. enterica_ YigF in preventing the dehydatase-dependent inhibition of IlvE [3]. Additionally, _S. enterica_ YigF could be replaced by human UK114 and other homologs in an in vitro assay of inhibition of phosphoribosylamine formation [2], and human UK114 can complement the defective phenotype of an _mmf1\(\Delta\)_ of _S. cerevisiae_[33]. Here, we report the first specificity study of goat UK114 showing that it is indeed endowed with RidA activity. Both snake venom l-amino acid oxidase (LAAO) and pig kidney d-amino acid oxidase (DAAO) were used to generate the imino acid substrates for testing UK114 activity. Moreover, studies on the conformational stability of UK114 revealed an impressive robustness of this enzyme. The results provide a basis to explore the function of RidA proteins in mammals, and may also contribute to re-evaluating the antigenic property of UK114 in terms of cross-reactivity among pan-allergens belonging to the RidA protein family and in the studies on the relationship between allergy and tumors.