title: Proton pump inhibitors drastically modify triosephosphate isomerase from Giardia lamblia at functional and structural levels, providing molecular leads in the design of new antigiardiasic drugs.
abstract: BACKGROUND
  Proton pump inhibitors (PPIs) are extensively used in clinical practice because of their effectiveness and safety. Omeprazole is one of the best-selling drugs worldwide and, with other PPIs, has been proposed to be potential drugs for the treatment of several diseases. We demonstrated that omeprazole shows cytotoxic effects in Giardia and concomitantly inactivates giardial triosephosphate isomerase (GlTIM). Therefore, we evaluated the efficiency of commercially available PPIs to inactivate this enzyme.
  
  
  METHODS
  We assayed the effect of PPIs on the GlTIM WT, single Cys mutants, and the human counterpart, following enzyme activity, thermal stability, exposure of hydrophobic regions, and susceptibility to limited proteolysis.
  
  
  RESULTS
  PPIs efficiently inactivated GlTIM; however, rabeprazole was the best inactivating drug and was nearly ten times more effective. The mechanism of inactivation by PPIs was through the modification of the Cys 222 residue. Moreover, there are important changes at the structural level, the thermal stability of inactivated-GlTIM was drastically diminished and the structural rigidity was lost, as observed by the exposure of hydrophobic regions and their susceptibility to limited proteolysis.
  
  
  CONCLUSIONS
  Our results demonstrate that rabeprazole is the most potent PPI for GlTIM inactivation and that all PPIs tested have substantial abilities to alter GITIM at the structural level, causing serious damage.
  
  
  CONCLUSIONS
  This is the first report demonstrating the effectiveness of commercial PPIs on a glycolytic parasitic enzyme, with structural features well known. This study is a step forward in the use and understanding the implicated mechanisms of new antigiardiasic drugs safe in humans.
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., México. Electronic address: itzheltorres@hotmail.com.
authors.forename: Itzhel
authors.initials: I
authors.lastname: García-Torres
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., México. Electronic address: ignaciodelamora@yahoo.com.mx.
authors.forename: Ignacio
authors.initials: I
authors.lastname: de la Mora-de la Mora
authors.affiliation: CONACyT Research Fellow-Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., México. Electronic address: jmarcialqu@conacyt.mx.
authors.forename: Jaime
authors.initials: J
authors.lastname: Marcial-Quino
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., México. Electronic address: saulmanzo@ciencias.unam.mx.
authors.forename: Saúl
authors.initials: S
authors.lastname: Gómez-Manzo
authors.affiliation: Laboratorio de Neurociencias, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., México. Electronic address: america_vc@yahoo.com.mx.
authors.forename: América
authors.initials: A
authors.lastname: Vanoye-Carlo
authors.affiliation: Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, 62209 Cuernavaca, Morelos, México. Electronic address: gabriel_navarrete@uaem.mx.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Navarrete-Vázquez
authors.affiliation: Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, 62209 Cuernavaca, Morelos, México. Electronic address: clbi_ff@uaem.mx.
authors.forename: Blanca
authors.initials: B
authors.lastname: Colín-Lozano
authors.affiliation: Hospital General Dr. Manuel Gea González, México, D.F., México. Electronic address: inpcochrane@gmail.com.
authors.forename: Pedro
authors.initials: P
authors.lastname: Gutiérrez-Castrellón
authors.affiliation: Colegio de Ciencias y Humanidades. Plantel Casa Libertad. Universidad Autónoma de la Ciudad de México, México, D.F., México. Electronic address: edgar.sierra@uacm.edu.com.
authors.forename: Edgar
authors.initials: E
authors.lastname: Sierra-Palacios
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., México. Electronic address: glv_1999@yahoo.com.
authors.forename: Gabriel
authors.initials: G
authors.lastname: López-Velázquez
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., México. Electronic address: sergioenriquezflores@gmail.com.
authors.forename: Sergio
authors.initials: S
authors.lastname: Enríquez-Flores
mesh_terms: D015195:Drug Design; D004795:Enzyme Stability; D016829:Giardia lamblia / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D013058:Mass Spectrometry; D054328:Proton Pump Inhibitors / Q000494:pharmacology*; D014305:Triose-Phosphate Isomerase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000502:physiology
chemical_list: D054328:Proton Pump Inhibitors; D014305:Triose-Phosphate Isomerase
keywords: Giardia lamblia; Proton pump inhibitors; Structural perturbation; Sulfenamide; Triosephosphate isomerase