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Open AccessArticle

Imine Deaminase Activity and Conformational Stability of UK114, the Mammalian Member of the Rid Protein Family Active in Amino Acid Metabolism

1
Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano, Italy
2
Dipartimento di Scienze per gli Alimenti, la Nutrizione e l’Ambiente, Università degli Studi di Milano, 20133 Milano, Italy
3
Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, 20133 Milano, Italy
*
Authors to whom correspondence should be addressed.
Int. J. Mol. Sci. 2018, 19(4), 945; https://doi.org/10.3390/ijms19040945
Received: 26 February 2018 / Revised: 16 March 2018 / Accepted: 18 March 2018 / Published: 22 March 2018
(This article belongs to the Special Issue Amino Acids Transport and Metabolism)
Reactive intermediate deaminase (Rid) protein family is a recently discovered group of enzymes that is conserved in all domains of life and is proposed to play a role in the detoxification of reactive enamines/imines. UK114, the mammalian member of RidA subfamily, was identified in the early 90s as a component of perchloric acid-soluble extracts from goat liver and exhibited immunomodulatory properties. Multiple activities were attributed to this protein, but its function is still unclear. This work addressed the question of whether UK114 is a Rid enzyme. Biochemical analyses demonstrated that UK114 hydrolyzes α-imino acids generated by l- or d-amino acid oxidases with a preference for those deriving from Ala > Leu = l-Met > l-Gln, whereas it was poorly active on l-Phe and l-His. Circular Dichroism (CD) analyses of UK114 conformational stability highlighted its remarkable resistance to thermal unfolding, even at high urea concentrations. The half-life of heat inactivation at 95 °C, measured from CD and activity data, was about 3.5 h. The unusual conformational stability of UK114 could be relevant in the frame of a future evaluation of its immunogenic properties. In conclusion, mammalian UK114 proteins are RidA enzymes that may play an important role in metabolism homeostasis also in these organisms. View Full-Text
Keywords: UK114; Rid family; metabolic damage; thermal stability; 2-aminoacrylate; imino acids; D-amino acid oxidase; l-amino acid oxidase UK114; Rid family; metabolic damage; thermal stability; 2-aminoacrylate; imino acids; D-amino acid oxidase; l-amino acid oxidase
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MDPI and ACS Style

Degani, G.; Barbiroli, A.; Regazzoni, L.; Popolo, L.; Vanoni, M.A. Imine Deaminase Activity and Conformational Stability of UK114, the Mammalian Member of the Rid Protein Family Active in Amino Acid Metabolism. Int. J. Mol. Sci. 2018, 19, 945.

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