title: Heme-iron utilization by Leptospira interrogans requires a heme oxygenase and a plastidic-type ferredoxin-NADP(+) reductase.
abstract: BACKGROUND
  Heme oxygenase catalyzes the conversion of heme to iron, carbon monoxide and biliverdin employing oxygen and reducing equivalents. This enzyme is essential for heme-iron utilization and contributes to virulence in Leptospira interrogans.
  
  
  METHODS
  A phylogenetic analysis was performed using heme oxygenases sequences from different organisms including saprophytic and pathogenic Leptospira species. L. interrogans heme oxygenase (LepHO) was cloned, overexpressed and purified. The structural and enzymatic properties of LepHO were analyzed by UV-vis spectrophotometry and (1)H NMR. Heme-degrading activity, ferrous iron release and biliverdin production were studied with different redox partners.
  
  
  RESULTS
  A plastidic type, high efficiently ferredoxin-NADP(+) reductase (LepFNR) provides the electrons for heme turnover by heme oxygenase in L. interrogans. This catalytic reaction does not require a ferredoxin. Moreover, LepFNR drives the heme degradation to completeness producing free iron and α-biliverdin as the final products. The phylogenetic divergence between heme oxygenases from saprophytic and pathogenic species supports the functional role of this enzyme in L. interrogans pathogenesis.
  
  
  CONCLUSIONS
  Heme-iron scavenging by LepHO in L. interrogans requires only LepFNR as redox partner. Thus, we report a new substrate of ferredoxin-NADP(+) reductases different to ferredoxin and flavodoxin, the only recognized protein substrates of this flavoenzyme to date. The results presented here uncover a fundamental step of heme degradation in L. interrogans.
  
  
  CONCLUSIONS
  Our findings contribute to understand the heme-iron utilization pathway in Leptospira. Since iron is required for pathogen survival and infectivity, heme degradation pathway may be relevant for therapeutic applications.
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, 2000 Rosario, Argentina.
authors.forename: Anabel
authors.initials: A
authors.lastname: Soldano
authors.affiliation: Department of Chemistry and Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Multidisciplinary Research Building, 2030 Becker Dr, Room 220 E, Lawrence, KS 66047, USA.
authors.forename: Huili
authors.initials: H
authors.lastname: Yao
authors.affiliation: Department of Chemistry and Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Multidisciplinary Research Building, 2030 Becker Dr, Room 220 E, Lawrence, KS 66047, USA.
authors.forename: Mario
authors.initials: M
authors.lastname: Rivera
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, 2000 Rosario, Argentina.
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Ceccarelli
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, 2000 Rosario, Argentina. Electronic address: catalano@ibr-conicet.gov.ar.
authors.forename: Daniela L
authors.initials: DL
authors.lastname: Catalano-Dupuy
keywords: Electron transfer; Ferredoxin-NADP(+) reductase; Heme oxygenase; Iron; Leptospira interrogans