title: Activity of intracellular phospholipase A1 and A2 in Giardia lamblia.
abstract: Neither phospholipase A1 (PLA A1) nor phospholipase A2 (PLA A2), nor their respective genes, have been identified in Giardia lamblia, even though they are essential for lipid metabolism in this parasite. A method to identify, isolate, and characterize these enzymes is needed. The activities of PLA A1 and PLA A2 were analyzed in a total extract (TE) and in vesicular (P30) and soluble (S30) subcellular fractions of G. lamblia trophozoites; the effects of several chemical and physicochemical factors on their activities were investigated. The assays were performed using substrate labeled with 14C, and the mass of the 14C-product was quantified. PLA A1 and PLA A2 activity was present in the TE and the P30 and S30 fractions, and it was dependent on pH and the concentrations of protein and Ca2+. In all trophozoite preparations, PLA A1 and PLA A2 activities were inhibited by ethylenediaminetetraacetic acid and Rosenthal's inhibitor. These results suggest that G. lamblia possesses several PLA A1 and PLA A2 isoforms that may be soluble or associated with membranes. In addition to participating in G. lamblia phospholipid metabolism, PLA A1 and PLA A2 could play important roles in the cytopathogenicity of this parasite.
authors.affiliation: División de Biología Celular y Molecular, Centro de Investigación Biomédica del Noreste, Instituto Mexicano del Seguro Social.
authors.forename: Javier
authors.initials: J
authors.lastname: Vargas-Villarreal
authors.forename: Brenda Leticia
authors.initials: BL
authors.lastname: Escobedo-Guajardo
authors.forename: Benito David
authors.initials: BD
authors.lastname: Mata-Cárdenas
authors.forename: Rebeca
authors.initials: R
authors.lastname: Palacios-Corona
authors.forename: Elva
authors.initials: E
authors.lastname: Cortes-Gutiérrez
authors.forename: Mario
authors.initials: M
authors.lastname: Morales-Vallarta
authors.forename: Adriana
authors.initials: A
authors.lastname: Sampayo-Reyes
authors.forename: Salvador
authors.initials: S
authors.lastname: Said-Fernández
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003470:Culture Media; D004492:Edetic Acid / Q000494:pharmacology; D016829:Giardia lamblia / Q000201:enzymology* / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism; D054466:Phospholipases A1 / Q000378:metabolism*; D054467:Phospholipases A2 / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D013228:Stearates; D013347:Subcellular Fractions / Q000201:enzymology; D053058:Trophozoites / Q000201:enzymology
chemical_list: D003470:Culture Media; D007527:Isoenzymes; D010743:Phospholipids; D013228:Stearates; C015161:Rosenthal's inhibitor; D004492:Edetic Acid; D054466:Phospholipases A1; D054467:Phospholipases A2; D002118:Calcium