On the Structure and Reaction Mechanism of Human Acireductone Dioxygenase. Issue 20 (11th January 2018)

• Record Type: Journal Article
• Authors: Miłaczewska, Anna; Kot, Ewa; Amaya, José A.; Makris, Thomas M.; Zając, Marcin; Korecki, Józef; Chumakov, Aleksandr; Trzewik, Bartosz; Kędracka‐Krok, Sylwia; Minor, Władek; Chruszcz, Maksymilian; Borowski, Tomasz
• Is Part Of: Chemistry. Volume 24:Issue 20(2018)
• Page Start: 5225
• Page End: 5237
• Publication Date: 2018-01-11
• Subjects: acireductone dioxygenase -- EPR spectroscopy -- Mössbauer spectroscopy -- protein structures -- reaction mechanisms; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201704617
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Acireductone dioxygenase (ARD) is an intriguing enzyme from the methionine salvage pathway that is capable of catalysing two different oxidation reactions with the same substrate depending on the type of the metal ion in the active site. To date, the structural information regarding the ARD–acireductone complex is limited and possible reaction mechanisms are still under debate. The results of joint experimental and computational studies undertaken to advance knowledge about ARD are reported. The crystal structure of an ARD from Homo sapiens was determined with selenomethionine. EPR spectroscopy suggested that binding acireductone triggers one protein residue to dissociate from Fe 2+, which allows NO (and presumably O2 ) to bind directly to the metal. Mössbauer spectroscopic data (interpreted with the aid of DFT calculations) was consistent with bidentate binding of acireductone to Fe 2+ and concomitant dissociation of His88 from the metal. Major features of Fe vibrational spectra obtained for the native enzyme and upon addition of acireductone were reproduced by QM/MM calculations for the proposed models. A computational (QM/MM) study of the reaction mechanisms suggests that Fe 2+ promotes O−O bond homolysis, which elicits cleavage of the C1−C2 bond of the substrate. Higher M 3+ /M 2+ redox potentials of other divalent metals do not support this pathway, and instead the reaction proceeds similarly to the key reaction step in the quercetin 2, 3‐dioxygenase mechanism. Abstract : h ARD working enzyme ! Experimental and computational studies of acireductone dioxygenase (ARD) from the methionine salvage pathway suggested reaction mechanisms catalysed by two isoforms: Fe 2+ promotes O−O homolysis and subsequent C1−C2 bond cleavage of the acireductone substrate, whereas Ni 2+ promotes a concerted O−O, C1−C2 and C2−C3 bond heterolysis (see figure).