title: S-Adenosyl-l-methionine Modulates CO and NO• Binding to the Human H2S-generating Enzyme Cystathionine β-Synthase.
abstract: Cystathionine β-synthase (CBS) is a key enzyme in human (patho)physiology with a central role in hydrogen sulfide metabolism. The enzyme is composed of a pyridoxal 5'-phosphate-binding catalytic domain, flanked by the following two domains: a heme-binding N-terminal domain and a regulatory C-terminal domain binding S-adenosyl-l-methionine (AdoMet). CO or NO(•) binding at the ferrous heme negatively modulates the enzyme activity. Conversely, AdoMet binding stimulates CBS activity. Here, we provide experimental evidence for a functional communication between the two domains. We report that AdoMet binding significantly enhances CBS inhibition by CO. Consistently, we observed increased affinity (∼5-fold) and faster association (∼10-fold) of CO to the ferrous heme at physiological AdoMet concentrations. NO(•) binding to reduced CBS was also enhanced by AdoMet, although to a lesser extent (∼2-fold higher affinity) as compared with CO. Importantly, CO and NO(•) binding was unchanged by AdoMet in a truncated form of CBS lacking the C-terminal regulatory domain. These unprecedented observations demonstrate that CBS activation by AdoMet puzzlingly sensitizes the enzyme toward inhibition by exogenous ligands, like CO and NO(•). This further supports the notion that CBS regulation is a complex process, involving the concerted action of multiple physiologically relevant effectors.
authors.affiliation: From the Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2781-156 Oeiras, Portugal, jvicente@itqb.unl.pt.
authors.forename: João B
authors.initials: JB
authors.lastname: Vicente
authors.affiliation: the Metabolism and Genetics Group, Research Institute for Medicines, Faculty of Pharmacy, University of Lisbon, 1649-003 Lisbon, Portugal.
authors.forename: Henrique G
authors.initials: HG
authors.lastname: Colaço
authors.affiliation: the Department of Biochemical Sciences and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, I-00185 Rome, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Sarti
authors.affiliation: the Metabolism and Genetics Group, Research Institute for Medicines, Faculty of Pharmacy, University of Lisbon, 1649-003 Lisbon, Portugal, the Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, 1640-003 Lisbon, Portugal, and.
authors.forename: Paula
authors.initials: P
authors.lastname: Leandro
authors.affiliation: the Institute of Molecular Biology and Pathology, National Research Council of Italy, I-00185 Rome, Italy alessandro.giuffre@uniroma1.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Giuffrè
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism*; D003541:Cystathionine beta-Synthase / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D012436:S-Adenosylmethionine / Q000494:pharmacology*
chemical_list: D009569:Nitric Oxide; D006418:Heme; D012436:S-Adenosylmethionine; D002248:Carbon Monoxide; D008715:Methionine; D003541:Cystathionine beta-Synthase
keywords: S-adenosylmethionine; allosteric regulation; carbon monoxide; heme; hydrogen sulfide; nitric oxide; signal transduction