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Tremblay-Laganière C, Michaud C, Abourjaili-Bilodeau R, Cabezas A, Canales J, Costas MJ, Ribeiro JM, Leclerc-Blain J, Touzot F, Haddad E, Teira P, Duval M, Onoufriadis A, Meunier B, Cameselle JC, Campeau PM. Homozygous variant in TKFC abolishing triokinase activities is associated with isolated immunodeficiency. J Med Genet 2024:jmg-2024-109853. [PMID: 38697782 DOI: 10.1136/jmg-2024-109853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 04/11/2024] [Indexed: 05/05/2024]
Abstract
BACKGROUND Triokinase and FMN cyclase (TKFC) is a bifunctional enzyme involved in fructose metabolism. Triokinase catalyses the phosphorylation of fructose-derived glyceraldehyde (GA) and exogenous dihydroxyacetone (DHA), while FMN cyclase generates cyclic FMN. TKFC regulates the antiviral immune response by interacting with IFIH1 (MDA5). Previously reported pathogenic variants in TKFC are associated with either a multisystemic disease or isolated hypotrichosis with loose anagen hairs. METHODS Whole-exome sequencing identified a homozygous novel variant in TKFC (c.1624G>A; p.Gly542Arg) in an individual with a complex primary immunodeficiency disorder. The variant was characterised using enzymatic assays and yeast studies of mutant recombinant proteins. RESULTS The individual presented with chronic active Epstein-Barr virus disease and multiple bacterial and viral infections. Clinical investigations revealed hypogammaglobulinaemia, near absent natural killer cells and decreased memory B cells. Enzymatic assays showed that this variant displayed defective DHA and GA kinase activity while maintaining FMN cyclase activity. An allogenic bone marrow transplantation corrected the patient's immunodeficiency. CONCLUSION Our report suggests that TKFC may have a role in the immunological system. The pathological features associated with this variant are possibly linked with DHA/GA kinase inactivation through a yet an unknown mechanism. This report thus adds a possible new pathway of immunometabolism to explore further.
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Affiliation(s)
| | - Coralie Michaud
- Research Centre, CHU Sainte-Justine, Montréal, Québec, Canada
| | | | - Alicia Cabezas
- Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz, Spain
| | - José Canales
- Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz, Spain
| | - María Jesús Costas
- Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz, Spain
| | - João M Ribeiro
- Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz, Spain
| | | | - Fabien Touzot
- Department of Pediatrics, CHU Sainte-Justine, Montréal, Québec, Canada
| | - Elie Haddad
- Pediatrics, University of Montreal, Montréal, Québec, Canada
| | - Pierre Teira
- Department of Pediatrics, CHU Sainte-Justine, Montréal, Québec, Canada
| | - Michel Duval
- Department of Pediatrics, CHU Sainte-Justine, Montréal, Québec, Canada
| | | | - Brigitte Meunier
- Institute for Integrative Biology of the Cell (I2BC), Paris-Saclay University, Gif-sur-Yvette, France
| | - José Carlos Cameselle
- Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz, Spain
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Ribeiro JM, Costas MJ, Cabezas A, Meunier B, Onoufriadis A, Cameselle JC. The TKFC Ala185Thr variant, reported as "null" for fructose metabolism, is fully active as triokinase. FEBS Lett 2022; 596:1453-1457. [PMID: 35114011 DOI: 10.1002/1873-3468.14309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 01/30/2022] [Indexed: 11/11/2022]
Abstract
TKFC-encoded triokinase catalyzes glyceraldehyde phosphorylation in fructose metabolism and favors lipogenesis in mice. In Tkfc knockouts or knockdowns, fructose oxidation predominates over lipogenesis. The highly-prevalent human variant Ala185Thr-TKFC has been reported to be "null" for fructose metabolism, since Ala185-TKFC rescues the mouse TKFC-deficient phenotype, whereas Ala185Thr-TKFC does not. Such report implies that most humans would display a non-canonical fructose metabolism, but it ignores the well-characterized triokinase activity of Ala185Thr-TKFC. Here, earlier evidence is summarized, along with new evidence that both human variants are equally active in yeast. Therefore, future research on triokinase in the context of human fructose metabolism should consider that Ala185Thr-TKFC is not biochemically "null".
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Affiliation(s)
- João M Ribeiro
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, Badajoz, Spain
| | - María Jesús Costas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, Badajoz, Spain
| | - Alicia Cabezas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, Badajoz, Spain
| | - Brigitte Meunier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Alexandros Onoufriadis
- St John's Institute of Dermatology, School of Basic and Medical Biosciences, King's College London, London, UK
| | - José Carlos Cameselle
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, Badajoz, Spain
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Viecenz JM, Garavaglia PA, Tasso LM, Maidana CG, Bautista Cannata JJ, García GA. Identification and biochemical characterization of an ATP-dependent dihydroxyacetone kinase from Trypanosoma cruzi. Exp Parasitol 2021; 231:108178. [PMID: 34767777 DOI: 10.1016/j.exppara.2021.108178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 10/12/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022]
Abstract
Dihydroxyacetone (DHA) can be used as an energy source by many cell types; however, it is toxic at high concentrations. The enzyme dihydroxyacetone kinase (DAK) has shown to be involved in DHA detoxification and osmoregulation. Among protozoa of the genus Trypanosoma, T. brucei, which causes sleeping sickness, is highly sensitive to DHA and does not have orthologous genes to DAK. Conversely, T. cruzi, the etiological agent of Chagas Disease, has two putative ATP-dependent DAK (TcDAKs) sequences in its genome. Here we show that T. cruzi epimastigote lysates present a DAK specific activity of 27.1 nmol/min/mg of protein and that this form of the parasite is able to grow in the presence of 2 mM DHA. TcDAK gene was cloned and the recombinant enzyme (recTcDAK) was expressed in Escherichia coli. An anti-recTcDAK serum reacted with a protein of the expected molecular mass of 61 kDa in epimastigotes. recTcDAK presented maximal activity using Mg+2, showing a Km of 6.5 μM for DHA and a K0.5 of 124.7 μM for ATP. As it was reported for other DAKs, recTcDAK activity was inhibited by FAD with an IC50 value of 0.33 mM. In conclusion, TcDAK is the first DAK described in trypanosomatids confirming another divergent metabolism between T. brucei and T. cruzi.
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Affiliation(s)
- Juan Matías Viecenz
- Instituto Nacional de Parasitología "Dr. Mario Fatala Chaben"-ANLIS "Dr. Carlos G. Malbrán". Paseo Colón 568, Buenos Aires, (1063), Argentina
| | - Patricia Andrea Garavaglia
- Instituto Nacional de Parasitología "Dr. Mario Fatala Chaben"-ANLIS "Dr. Carlos G. Malbrán". Paseo Colón 568, Buenos Aires, (1063), Argentina
| | - Laura Mónica Tasso
- Instituto Nacional de Parasitología "Dr. Mario Fatala Chaben"-ANLIS "Dr. Carlos G. Malbrán". Paseo Colón 568, Buenos Aires, (1063), Argentina
| | - Cristina Graciela Maidana
- Instituto Nacional de Parasitología "Dr. Mario Fatala Chaben"-ANLIS "Dr. Carlos G. Malbrán". Paseo Colón 568, Buenos Aires, (1063), Argentina
| | - Joaquín Juan Bautista Cannata
- Instituto de Investigaciones Biotecnológicas (IIB-INTECH) "Dr. Rodolfo A. Ugalde", Universidad Nacional de General San Martín-CONICET, San Martín, (1650), Prov. Buenos Aires, Argentina
| | - Gabriela Andrea García
- Instituto Nacional de Parasitología "Dr. Mario Fatala Chaben"-ANLIS "Dr. Carlos G. Malbrán". Paseo Colón 568, Buenos Aires, (1063), Argentina.
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Onoufriadis A, Cabezas A, Ng JCF, Canales J, Costas MJ, Ribeiro JM, Rodrigues JR, McAleer MA, Castelo-Soccio L, Simpson MA, Fraternali F, Irvine AD, Cameselle JC, McGrath JA. Autosomal recessive hypotrichosis with loose anagen hairs associated with TKFC mutations. Br J Dermatol 2020; 184:935-943. [PMID: 32790068 DOI: 10.1111/bjd.19481] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/07/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Loose anagen hair is a rare form of impaired hair anchorage in which anagen hairs that lack inner and outer root sheaths can be gently and painlessly plucked from the scalp. This condition usually occurs in children and is often self-limiting. A genetic basis for the disorder has been suggested but not proven. A better understanding the aetiology of loose anagen hair may improve prevention and treatment strategies. OBJECTIVES To identify a possible genetic basis of loose anagen hair using next-generation DNA sequencing and functional analysis of variants identified. METHODS In this case study, whole-exome sequencing analysis of a pedigree with one affected individual with features of loose anagen hair was performed. RESULTS The patient was found to be compound heterozygous for two single-nucleotide substitutions in TKFC resulting in the following missense mutations: c.574G> C (p.Gly192Arg) and c.682C> T (p.Arg228Trp). Structural analysis of human TKFC showed that both mutations are located near the active site cavity. Kinetic assays of recombinant proteins bearing either of these amino acid substitutions showed almost no dihydroxyacetone kinase or D-glyceraldehyde kinase activity, and FMN cyclase activity reduced to just 10% of wildtype catalytic activity. CONCLUSIONS TKFC missense mutations may predispose to the development of loose anagen hairs. Identification of this new biochemical pathobiology expands the metabolic and genetic basis of hypotrichosis.
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Affiliation(s)
- A Onoufriadis
- St John's Institute of Dermatology, School of Basic and Medical Biosciences, Guy's Hospital, King's College London, London, UK
| | - A Cabezas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - J C F Ng
- Randall Centre for Cell and Molecular Biophysics, Guy's Hospital, King's College London, London, UK
| | - J Canales
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - M J Costas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - J M Ribeiro
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - J R Rodrigues
- Laboratório Associado LSRE-LCM, Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Leiria, Leiria, Portugal
| | - M A McAleer
- Paediatric Dermatology, Children's Health Ireland at Crumlin, Dublin, Ireland
| | - L Castelo-Soccio
- Pediatric Dermatology, Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - M A Simpson
- Department of Medical and Molecular Genetics, School of Basic and Medical Biosciences, Guy's Hospital, King's College London, London, UK
| | - F Fraternali
- Randall Centre for Cell and Molecular Biophysics, Guy's Hospital, King's College London, London, UK
| | - A D Irvine
- Paediatric Dermatology, Children's Health Ireland at Crumlin, Dublin, Ireland.,Clinical Medicine, Trinity College Dublin, Dublin, Ireland
| | - J C Cameselle
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - J A McGrath
- St John's Institute of Dermatology, School of Basic and Medical Biosciences, Guy's Hospital, King's College London, London, UK
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Rodrigues JR, Couto A, Cabezas A, Pinto RM, Ribeiro JM, Canales J, Costas MJ, Cameselle JC. Bifunctional homodimeric triokinase/FMN cyclase: contribution of protein domains to the activities of the human enzyme and molecular dynamics simulation of domain movements. J Biol Chem 2014; 289:10620-10636. [PMID: 24569995 DOI: 10.1074/jbc.m113.525626] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mammalian triokinase, which phosphorylates exogenous dihydroxyacetone and fructose-derived glyceraldehyde, is neither molecularly identified nor firmly associated to an encoding gene. Human FMN cyclase, which splits FAD and other ribonucleoside diphosphate-X compounds to ribonucleoside monophosphate and cyclic X-phosphodiester, is identical to a DAK-encoded dihydroxyacetone kinase. This bifunctional protein was identified as triokinase. It was modeled as a homodimer of two-domain (K and L) subunits. Active centers lie between K1 and L2 or K2 and L1: dihydroxyacetone binds K and ATP binds L in different subunits too distant (≈ 14 Å) for phosphoryl transfer. FAD docked to the ATP site with ribityl 4'-OH in a possible near-attack conformation for cyclase activity. Reciprocal inhibition between kinase and cyclase reactants confirmed substrate site locations. The differential roles of protein domains were supported by their individual expression: K was inactive, and L displayed cyclase but not kinase activity. The importance of domain mobility for the kinase activity of dimeric triokinase was highlighted by molecular dynamics simulations: ATP approached dihydroxyacetone at distances below 5 Å in near-attack conformation. Based upon structure, docking, and molecular dynamics simulations, relevant residues were mutated to alanine, and kcat and Km were assayed whenever kinase and/or cyclase activity was conserved. The results supported the roles of Thr(112) (hydrogen bonding of ATP adenine to K in the closed active center), His(221) (covalent anchoring of dihydroxyacetone to K), Asp(401) and Asp(403) (metal coordination to L), and Asp(556) (hydrogen bonding of ATP or FAD ribose to L domain). Interestingly, the His(221) point mutant acted specifically as a cyclase without kinase activity.
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Affiliation(s)
- Joaquim Rui Rodrigues
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain; Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Leiria, P-2411-901 Leiria, Portugal
| | - Ana Couto
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain
| | - Alicia Cabezas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain
| | - Rosa María Pinto
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain
| | - João Meireles Ribeiro
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain
| | - José Canales
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain
| | - María Jesús Costas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain
| | - José Carlos Cameselle
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, E-06006 Badajoz, Spain.
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Rhee HW, Choi SJ, Yoo SH, Jang YO, Park HH, Pinto RM, Cameselle JC, Sandoval FJ, Roje S, Han K, Chung DS, Suh J, Hong JI. A bifunctional molecule as an artificial flavin mononucleotide cyclase and a chemosensor for selective fluorescent detection of flavins. J Am Chem Soc 2009; 131:10107-12. [PMID: 19569646 DOI: 10.1021/ja9018012] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Flavins, comprising flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and riboflavin (RF, vitamin B(2)), play important roles in numerous redox reactions such as those taking place in the electron-transfer chains of mitochondria in all eukaryotes and of plastids in plants. A selective chemosensor for flavins would be useful not only in the investigation of metabolic processes but also in the diagnosis of diseases related to flavins; such a sensor is presently unavailable. Herein, we report the first bifunctional chemosensor (PTZ-DPA) for flavins. PTZ-DPA consists of bis(Zn(2+)-dipicolylamine) and phenothiazine. Bis(Zn(2+)-dipicolylamine) (referred to here as XyDPA) was found to be an excellent catalyst in the conversion of FAD into cyclic FMN (riboflavin 4',5'-cyclic phosphate, cFMN) under physiological conditions, even at pH 7.4 and 27 degrees C, with less than 1 mol % of substrate. Utilizing XyDPA's superior function as an artificial FMN cyclase and phenothiazine as an electron donor able to quench the fluorescence of an isoalloxazine ring, PTZ-DPA enabled selective fluorescent discrimination of flavins (FMN, FAD, and RF): FAD shows ON(+), FMN shows OFF(-), and RF shows NO(0) fluorescence changes upon the addition of PTZ-DPA. With this selective sensing property, PTZ-DPA is applicable to real-time fluorescent monitoring of riboflavin kinase (RF to FMN), alkaline phosphatase (FMN to RF), and FAD synthetase (FMN to FAD).
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Affiliation(s)
- Hyun-Woo Rhee
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea
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Sánchez-Moreno I, Iturrate L, Martín-Hoyos R, Jimeno ML, Mena M, Bastida A, García-Junceda E. From kinase to cyclase: an unusual example of catalytic promiscuity modulated by metal switching. Chembiochem 2009; 10:225-9. [PMID: 19058275 DOI: 10.1002/cbic.200800573] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Israel Sánchez-Moreno
- Departamento de Química Orgánica Biológica, Instituto de Química Orgánica General, CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
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Cabezas A, Costas MJ, Pinto RM, Couto A, Cameselle JC. Identification of human and rat FAD-AMP lyase (cyclic FMN forming) as ATP-dependent dihydroxyacetone kinases. Biochem Biophys Res Commun 2005; 338:1682-9. [PMID: 16289032 DOI: 10.1016/j.bbrc.2005.10.142] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2005] [Accepted: 10/24/2005] [Indexed: 10/25/2022]
Abstract
Rat liver FAD-AMP lyase or FMN cyclase is the only known enzymatic source of the unusual flavin nucleotide riboflavin 4',5'-cyclic phosphate. To determine its molecular identity, a peptide-mass fingerprint of the purified rat enzyme was obtained. It pointed to highly related, mammalian hypothetical proteins putatively classified as dihydroxyacetone (Dha) kinases due to weaker homologies to biochemically proven Dha kinases of plants, yeasts, and bacteria. The human protein LOC26007 cDNA was used to design PCR primers. The product amplified from human brain cDNA was cloned, sequenced (GenBank Accession No. ), and found to differ from protein LOC26007 cDNA by three SNPs. Its heterologous expression yielded a protein active both as FMN cyclase and ATP-dependent Dha kinase, each activity being inhibited by the substrate(s) of the other. Cyclase and kinase activities copurified from rat liver extracts. Evidence supports that a single protein sustains both activities, probably in a single active center. Putative Dha kinases from other mammals are likely to be FMN cyclases too. Future work will profit from the availability of the structure of Citrobacter freundii Dha kinase, which contains substrate-interacting residues conserved in human Dha kinase/FMN cyclase.
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Affiliation(s)
- Alicia Cabezas
- Unidad de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Extremadura, 06080 Badajoz, Spain
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Canales J, Cabezas A, Pinto RM, Cameselle JC. Fluorimetric HPLC detection of endogenous riboflavin 4',5'-cyclic phosphate in rat liver at nanomolar concentrations. Anal Biochem 2005; 341:214-9. [PMID: 15907866 DOI: 10.1016/j.ab.2005.01.060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2004] [Indexed: 10/25/2022]
Abstract
We have investigated the biological occurrence of riboflavin 4',5'-cyclic phosphate (cyclic FMN or cFMN), the flavin product known to be formed in vitro from FAD by the rat liver enzyme FAD-AMP lyase (cyclizing) or FMN cyclase (EC 4.6.1.15). The expected difficulties were the low concentration of the compound, the tendency of the more abundant FAD to decompose chemically to cFMN, and the acid lability of cFMN itself. A protocol was devised to prepare deproteinized rat liver extracts, avoiding conditions prone to the chemical formation of cFMN and making exposure to conditions of cFMN degradation as short as possible. In these extracts, cFMN was assayed by HPLC with fluorimetric detection. The identity of liver cFMN was confirmed by its HPLC separation from other known flavins, its coelution with authentic cFMN, and its susceptibility to acid degradation, yielding a mixture of 5'-FMN and 4'-FMN. The amount of total cFMN recovered in the liver extracts was 22+/-11 pmol/g fresh tissue. Careful control experiments were performed to rule out the possibility that this could be a chemical product of FAD degradation during extract preparation. These controls indicated that, on average, 97% of the measured extract concentration of cFMN, i.e., about 21+/-10 pmol/g, was already present in the liver at the beginning of the process and was extracted from the tissue. This figure is likely to be an underestimation of the hepatic content, as indicated by control experiments.
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Affiliation(s)
- José Canales
- Unidad de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Extremadura, 06080 Badajoz, Spain
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