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Leone P, Galluccio M, Brizio C, Barbiroli A, Iametti S, Indiveri C, Barile M. The hidden side of the human FAD synthase 2. Int J Biol Macromol 2019; 138:986-995. [PMID: 31351152 DOI: 10.1016/j.ijbiomac.2019.07.138] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 07/22/2019] [Accepted: 07/23/2019] [Indexed: 11/16/2022]
Abstract
FAD synthase, the last enzyme of the pathway converting riboflavin to FAD, exists in humans in different isoforms, with isoforms 1, 2 and 6 being characterized at the functional and molecular levels. Isoform 2, the cytosolic and most abundant FADS, consists of two domains: a PAPS reductase C-terminus domain (here named FADSy) responsible for FAD synthesis, and an N-terminus molybdopterin-binding resembling domain (MPTb - here named FADHy), whose FAD hydrolytic activity is hidden unless both Co2+ and chemical mercurial reagents are added to the enzyme. To investigate the hFADS2 hydrolytic function under conditions closer to the physiological context, the hydrolytic activity was further characterized. Co2+ induced FAD hydrolysis was strongly stimulated in the presence of K+, reaching a Vmax higher than that of FAD synthesis. The pH dependence together with the inhibition of the hydrolysis by NaF and KI allow excluding that the reaction occurs via a NUDIX type catalysis. The K0.5 for K+ or Co2+ was 7.2 or 0.035 mM, respectively. Other monovalent or divalent cations can partially substitute K+ or Co2+. Reduced glutathione stimulated whereas NADH inhibited the hydrolytic activity. The latter aspects correlate with an interconnection of the homeostasis of NAD and FAD.
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Affiliation(s)
- Piero Leone
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, via Orabona 4 -, 70126 Bari, Italy; Department of Biology, Ecology and Earth Sciences (DiBEST), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, via P. Bucci 4c, , 87036 Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department of Biology, Ecology and Earth Sciences (DiBEST), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, via P. Bucci 4c, , 87036 Arcavacata di Rende, Italy
| | - Carmen Brizio
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, via Orabona 4 -, 70126 Bari, Italy
| | - Alberto Barbiroli
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente (DeFENS), Università degli Studi di Milano, via Celoria 2, I-20133 Milano, Italy
| | - Stefania Iametti
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente (DeFENS), Università degli Studi di Milano, via Celoria 2, I-20133 Milano, Italy
| | - Cesare Indiveri
- Department of Biology, Ecology and Earth Sciences (DiBEST), Unit of Biochemistry and Molecular Biotechnology, University of Calabria, via P. Bucci 4c, , 87036 Arcavacata di Rende, Italy; Institute of Biomembranes, Bioenergetics and Molecular Biotechnology (IBIOM) - CNR, via Giovanni Amendola 165/A, 70126 Bari, Italy
| | - Maria Barile
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, via Orabona 4 -, 70126 Bari, Italy.
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Giancaspero TA, Galluccio M, Miccolis A, Leone P, Eberini I, Iametti S, Indiveri C, Barile M. Human FAD synthase is a bi-functional enzyme with a FAD hydrolase activity in the molybdopterin binding domain. Biochem Biophys Res Commun 2015; 465:443-9. [PMID: 26277395 DOI: 10.1016/j.bbrc.2015.08.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 08/09/2015] [Indexed: 02/05/2023]
Abstract
FAD synthase (FMN:ATP adenylyl transferase, FMNAT or FADS, EC 2.7.7.2) is involved in the biochemical pathway for converting riboflavin into FAD. Human FADS exists in different isoforms. Two of these have been characterized and are localized in different subcellular compartments. hFADS2 containing 490 amino acids shows a two domain organization: the 3'-phosphoadenosine-5'-phosphosulfate (PAPS) reductase domain, that is the FAD-forming catalytic domain, and a resembling molybdopterin-binding (MPTb) domain. By a multialignment of hFADS2 with other MPTb containing proteins of various organisms from bacteria to plants, the critical residues for hydrolytic function were identified. A homology model of the MPTb domain of hFADS2 was built, using as template the solved structure of a T. acidophilum enzyme. The capacity of hFADS2 to catalyse FAD hydrolysis was revealed. The recombinant hFADS2 was able to hydrolyse added FAD in a Co(2+) and mersalyl dependent reaction. The recombinant PAPS reductase domain is not able to perform the same function. The mutant C440A catalyses the same hydrolytic function of WT with no essential requirement for mersalyl, thus indicating the involvement of C440 in the control of hydrolysis switch. The enzyme C440A is also able to catalyse hydrolysis of FAD bound to the PAPS reductase domain, which is quantitatively converted into FMN.
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Affiliation(s)
- Teresa Anna Giancaspero
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "A. Moro", via Orabona 4, I-70126, Bari, Italy.
| | - Michele Galluccio
- Dipartimento DiBEST, Biologia, Ecologia, Scienze della Terra, Unità di Biochimica e Biotecnologie Molecolari, Università della Calabria, via Bucci 4c, I-87036, Arcavacata di Rende, Italy.
| | - Angelica Miccolis
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "A. Moro", via Orabona 4, I-70126, Bari, Italy.
| | - Piero Leone
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "A. Moro", via Orabona 4, I-70126, Bari, Italy.
| | - Ivano Eberini
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, via Balzaretti 9, I-20133, Milano, Italy.
| | - Stefania Iametti
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano, via Celoria 2, I-20133, Milano, Italy.
| | - Cesare Indiveri
- Dipartimento DiBEST, Biologia, Ecologia, Scienze della Terra, Unità di Biochimica e Biotecnologie Molecolari, Università della Calabria, via Bucci 4c, I-87036, Arcavacata di Rende, Italy.
| | - Maria Barile
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "A. Moro", via Orabona 4, I-70126, Bari, Italy.
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Miccolis A, Galluccio M, Nitride C, Giancaspero TA, Ferranti P, Iametti S, Indiveri C, Bonomi F, Barile M. Significance of redox-active cysteines in human FAD synthase isoform 2. Biochim Biophys Acta 2014; 1844:2086-95. [PMID: 25135855 DOI: 10.1016/j.bbapap.2014.08.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/30/2014] [Accepted: 08/08/2014] [Indexed: 11/22/2022]
Abstract
FAD synthase (FMN:ATP adenylyl transferase, FMNAT or FADS, EC 2.7.7.2) is the last enzyme in the pathway converting riboflavin into FAD. In humans, FADS is localized in different subcellular compartments and exists in different isoforms. Isoform 2 (490-amino acids) is organized in two domains: the 3'-phosphoadenosine-5'-phosphosulfate (PAPS) reductase domain, that is the FAD-forming catalytic domain, and one resembling a molybdopterin-binding (MPTb) domain, with a hypothetical regulatory role. hFADS2 contains ten Cys residues, seven of which located in the PAPS reductase domain, with a possible involvement either in FAD synthesis or in FAD delivery to cognate apo-flavoproteins. A homology model of the PAPS reductase domain of hFADS2 revealed a co-ordinated network among the Cys residues in this domain. In this model, C312 and C303 are very close to the flavin substrate, consistent with a significantly lowered FAD synthesis rate in C303A and C312A mutants. FAD synthesis is also inhibited by thiol-blocking reagents, suggesting the involvement of free cysteines in the hFADS2 catalytic cycle. Mass spectrometry measurements and titration with thiol reagents on wt hFADS2 and on several individual cysteine/alanine mutants allowed us to detect two stably reduced cysteines (C139 and C241, one for each protein domain), two stable disulfide bridges (C399-C402, C303-C312, both in the PAPS domain), and two unstable disulfides (C39-C50; C440-C464). Whereas the C39-C50 unstable disulfide is located in the MPTb domain and appears to have no catalytic relevance, a cysteine-based redox switch may involve formation and breakdown of a disulfide between C440 and C464 in the PAPS domain.
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