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Schwahn BC, van Spronsen F, Misko A, Pavaine J, Holmes V, Spiegel R, Schwarz G, Wong F, Horman A, Pitt J, Sass JO, Lubout C. Consensus guidelines for the diagnosis and management of isolated sulfite oxidase deficiency and molybdenum cofactor deficiencies. J Inherit Metab Dis 2024; 47:598-623. [PMID: 38627985 DOI: 10.1002/jimd.12730] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 02/29/2024] [Accepted: 03/07/2024] [Indexed: 07/18/2024]
Abstract
Sulfite intoxication is the hallmark of four ultrarare disorders that are caused by impaired sulfite oxidase activity due to genetic defects in the synthesis of the molybdenum cofactor or of the apoenzyme sulfite oxidase. Delays on the diagnosis of these disorders are common and have been caused by their unspecific presentation of acute neonatal encephalopathy with high early mortality, followed by the evolution of dystonic cerebral palsy and also by the lack of easily available and reliable diagnostic tests. There is significant variation in survival and in the quality of symptomatic management of affected children. One of the four disorders, molybdenum cofactor deficiency type A (MoCD-A) has recently become amenable to causal treatment with synthetic cPMP (fosdenopterin). The evidence base for the rational use of cPMP is very limited. This prompted the formulation of these clinical guidelines to facilitate diagnosis and support the management of patients. The guidelines were developed by experts in diagnosis and treatment of sulfite intoxication disorders. It reflects expert consensus opinion and evidence from a systematic literature search.
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Affiliation(s)
- Bernd C Schwahn
- Division of Evolution & Genomic Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
- Manchester Centre for Genomic Medicine, Saint Mary's Hospital, Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - Francjan van Spronsen
- Department of Metabolic Diseases, Beatrix Children's, University Medical Center (UMC) Groningen, Groningen, Netherlands
| | - Albert Misko
- Massachusetts General Hospital Department of Neurology, Boston, Massachusetts, USA
| | - Julija Pavaine
- Department of Paediatric Radiology, Royal Manchester Children's Hospital, Manchester University Hospitals NHS Foundation Trust, University of Manchester, Manchester, UK
- Division of Informatics, Imaging & Data Sciences, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Victoria Holmes
- Willink Unit, Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Ronen Spiegel
- Department of Pediatrics Unit B, Emek Medical Center, Afula, Israel
| | | | - Flora Wong
- Monash Children's Hospital/Hudson Institute of Medical Research/Monash University, Melbourne, Victoria, Australia
| | | | - James Pitt
- Victorian Clinical Genetics Services, The Royal Children's Hospital, Parkville, Victoria, Australia
| | - Jörn Oliver Sass
- RG Inborn Error of Metabolism, Department of Natural Sciences & Institute for Functional Gene Analytics (IFGA), Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
| | - Charlotte Lubout
- Department of Metabolic Diseases, Beatrix Children's, University Medical Center (UMC) Groningen, Groningen, Netherlands
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Mendel RR, Schwarz G. The History of Animal and Plant Sulfite Oxidase-A Personal View. Molecules 2023; 28:6998. [PMID: 37836841 PMCID: PMC10574614 DOI: 10.3390/molecules28196998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 10/06/2023] [Accepted: 10/07/2023] [Indexed: 10/15/2023] Open
Abstract
Sulfite oxidase is one of five molybdenum-containing enzymes known in eukaryotes where it catalyzes the oxidation of sulfite to sulfate. This review covers the history of sulfite oxidase research starting out with the early years of its discovery as a hepatic mitochondrial enzyme in vertebrates, leading to basic biochemical and structural properties that have inspired research for decades. A personal view on sulfite oxidase in plants, that sulfates are assimilated for their de novo synthesis of cysteine, is presented by Ralf Mendel with numerous unexpected findings and unique properties of this single-cofactor sulfite oxidase localized to peroxisomes. Guenter Schwarz connects his research to sulfite oxidase via its deficiency in humans, demonstrating its unique role amongst all molybdenum enzymes in humans. In essence, in both the plant and animal kingdoms, sulfite oxidase represents an important player in redox regulation, signaling and metabolism, thereby connecting sulfur and nitrogen metabolism in multiple ways.
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Affiliation(s)
- Ralf R. Mendel
- Institute of Plant Biology, Technical University Braunschweig, Humboldtstrasse 1, 38106 Braunschweig, Germany
| | - Günter Schwarz
- Institute of Biochemistry, Department of Chemistry & Center for Molecular Medicine, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany;
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Enemark JH. Mechanistic complexities of sulfite oxidase: An enzyme with multiple domains, subunits, and cofactors. J Inorg Biochem 2023; 247:112312. [PMID: 37441922 DOI: 10.1016/j.jinorgbio.2023.112312] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 05/13/2023] [Accepted: 07/01/2023] [Indexed: 07/15/2023]
Abstract
Sulfite oxidase (SO) deficiency, an inherited disease that causes severe neonatal neurological problems and early death, arises from defects in the biosynthesis of the molybdenum cofactor (Moco) (general sulfite oxidase deficiency) or from inborn errors in the SUOX gene for SO (isolated sulfite oxidase deficiency, ISOD). The X-ray structure of the highly homologous homonuclear dimeric chicken sulfite oxidase (cSO) provides a template for locating ISOD mutation sites in human sulfite oxidase (hSO). Catalysis occurs within an individual subunit of hSO, but mutations that disrupt the hSO dimer are pathological. The catalytic cycle of SO involves five metal oxidation states (MoVI, MoV, MoIV, FeIII, FeII), two intramolecular electron transfer (IET) steps, and couples a two-electron oxygen atom transfer reaction at the Mo center with two one-electron transfers from the integral b-type heme to exogenous cytochrome c, the physiological oxidant. Several ISOD examples are analyzed using steady-state, stopped-flow, and laser flash photolysis kinetics and physical measurements of recombinant variants of hSO and native cSO. In the structure of cSO, Mo…Fe = 32 Å, much too long for efficient IET through the protein. Interdomain motion that brings the Mo and heme centers closer together to facilitate IET is supported indirectly by decreasing the length of the interdomain tether, by changes in the charges of surface residues of the Mo and heme domains, as well as by preliminary molecular dynamics calculations. However, direct dynamic measurements of interdomain motion are in their infancy.
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Affiliation(s)
- John H Enemark
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd, Tucson, AZ 85721-0041, United States of America.
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Ahmad M, Singla N, Bhadwal SS, Kaur S, Singh P, Kumar S. Differentiation of HSA and BSA and Instantaneous Detection of HSO 3 - Using Confined Space of Serum Albumins and Live Cell Imaging of Exogenous/Endogenous HSO 3. ACS OMEGA 2023; 8:2639-2647. [PMID: 36687064 PMCID: PMC9851030 DOI: 10.1021/acsomega.2c07163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
The limitations of prevailing probes for the detection of human serum albumin (HSA) and HSO3 - make it challenging to apprehend the cooperative effect of both HSA and HSO3 - in biological systems. Herein, we present a multi-responsive fluorescent probe MGTP, which distinguishes HSA from bovine serum albumin (BSA) through an ∼104-fold fluorescence enhancement at an emission maximum of 595 nm with HSA and only an ∼10-fold increase at an emission maximum of 615 nm with a shoulder at 680 nm with BSA. The absorbance spectrum of MGTP also discriminates HSA and BSA with the respective absorption maxima at 543 nm and at 580 nm. MGTP in the confined space of HSA or BSA undergoes instantaneous conjugate addition of HSO3 - and results in a ratiometric change in fluorescence intensity with diminishing of red fluorescence (600 nm) and emergence of green fluorescence (515 nm). MGTP in the absence of SAs does not react with HSO3 - in phosphate-buffered saline buffer and reacts sluggishly in the dimethyl sulfoxide-water 1:1 mixture. The limit of detection values for the detection of HSA and HSO3 - are 4 and 6.88 nM, respectively. The drug binding studies reveal that MGTP preferably confines itself at the bilirubin site of HSA. In MCF-7 cancer cells, MGTP is localized into mitochondria and reveals both exogenous and endogenous visualization of HSO3 - through a change in fluorescence from the red to green channel.
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Affiliation(s)
- Manzoor Ahmad
- Department
of Chemistry, Guru Nanak Dev University, Amritsar 143005, India
| | - Nancy Singla
- Department
of Chemistry, Guru Nanak Dev University, Amritsar 143005, India
| | - Siloni Singh Bhadwal
- Department
of Botanical and Environment Science, Guru
Nanak Dev University, Amritsar 143005, India
| | - Satwinderjeet Kaur
- Department
of Botanical and Environment Science, Guru
Nanak Dev University, Amritsar 143005, India
| | - Prabhpreet Singh
- Department
of Chemistry, Guru Nanak Dev University, Amritsar 143005, India
| | - Subodh Kumar
- Department
of Chemistry, Guru Nanak Dev University, Amritsar 143005, India
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Johannes L, Fu CY, Schwarz G. Molybdenum Cofactor Deficiency in Humans. Molecules 2022; 27:6896. [PMID: 36296488 PMCID: PMC9607355 DOI: 10.3390/molecules27206896] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 11/17/2022] Open
Abstract
Molybdenum cofactor (Moco) deficiency (MoCD) is characterized by neonatal-onset myoclonic epileptic encephalopathy and dystonia with cerebral MRI changes similar to hypoxic-ischemic lesions. The molecular cause of the disease is the loss of sulfite oxidase (SOX) activity, one of four Moco-dependent enzymes in men. Accumulating toxic sulfite causes a secondary increase of metabolites such as S-sulfocysteine and thiosulfate as well as a decrease in cysteine and its oxidized form, cystine. Moco is synthesized by a three-step biosynthetic pathway that involves the gene products of MOCS1, MOCS2, MOCS3, and GPHN. Depending on which synthetic step is impaired, MoCD is classified as type A, B, or C. This distinction is relevant for patient management because the metabolic block in MoCD type A can be circumvented by administering cyclic pyranopterin monophosphate (cPMP). Substitution therapy with cPMP is highly effective in reducing sulfite toxicity and restoring biochemical homeostasis, while the clinical outcome critically depends on the degree of brain injury prior to the start of treatment. In the absence of a specific treatment for MoCD type B/C and SOX deficiency, we summarize recent progress in our understanding of the underlying metabolic changes in cysteine homeostasis and propose novel therapeutic interventions to circumvent those pathological changes.
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Affiliation(s)
| | | | - Günter Schwarz
- Institute of Biochemistry, Department of Chemistry & Center for Molecular Medicine Cologne, University of Cologne, 50674 Cologne, Germany
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Molecular mechanism of intramolecular electron transfer in dimeric sulfite oxidase. J Biol Chem 2022; 298:101668. [PMID: 35120924 PMCID: PMC8908248 DOI: 10.1016/j.jbc.2022.101668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 12/02/2022] Open
Abstract
Sulfite oxidase (SOX) is a homodimeric molybdoheme enzyme that oxidizes sulfite to sulfate at the molybdenum center. Following substrate oxidation, molybdenum is reduced and subsequently regenerated by two sequential electron transfers (ETs) via heme to cytochrome c. SOX harbors both metals in spatially separated domains within each subunit, suggesting that domain movement is necessary to allow intramolecular ET. To address whether one subunit in a SOX dimer is sufficient for catalysis, we produced heterodimeric SOX variants with abolished sulfite oxidation by replacing the molybdenum-coordinating and essential cysteine in the active site. To further elucidate whether electrons can bifurcate between subunits, we truncated one or both subunits by deleting the heme domain. We generated three SOX heterodimers: (i) SOX/Mo with two active molybdenum centers but one deleted heme domain, (ii) SOX/Mo_C264S with one unmodified and one inactive subunit, and (iii) SOX_C264S/Mo harboring a functional molybdenum center on one subunit and a heme domain on the other subunit. Steady-state kinetics showed 50% SOX activity for the SOX/Mo and SOX/Mo_C264S heterodimers, whereas SOX_C264S/Mo activity was reduced by two orders of magnitude. Rapid reaction kinetics monitoring revealed comparable ET rates in SOX/Mo, SOX/Mo_C264S, and SOX/SOX, whereas in SOX_C264S/Mo, ET was strongly compromised. We also combined a functional SOX Mo domain with an inactive full-length SOX R217W variant and demonstrated interdimer ET that resembled SOX_C264S/Mo activity. Collectively, our results indicate that one functional subunit in SOX is sufficient for catalysis and that electrons derived from either Mo(IV) or Mo(V) follow this path.
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