title: Isolation and biochemical characterization of a thaumatin-like kiwi allergen.
abstract: BACKGROUND
  Kiwi fruit allergy, as well as its association with hypersensitivity to other foods and to pollen, has been extensively reported in the last few years. Several IgE-binding components have been detected in kiwi extract, but only one 30- kd allergen has been isolated; it was identified as actinidin (Act c 1). Recently, we have reported a 24-kd kiwi protein to be a potential major allergen in a group of patients with oral allergy syndrome (OAS).
  
  
  OBJECTIVE
  The aim of this study was to purify and characterize the 24-kd kiwi allergen biochemically.
  
  
  METHODS
  Seven polysensitized patients with OAS to kiwi were used in this study. The kiwi allergen was isolated by using a combination of gel permeation, ion exchange, and immobilized metal ion affinity chromatography. Its biochemical characterization included determination of its isoelectric point, molecular weight, N-terminal sequencing, concanavalin A -binding ability, digestibility in simulated gastric fluid, and antifungal activity. Western blotting, 2-dimensional PAGE immunoblotting, and skin prick tests were performed to characterize the isolated protein immunochemically.
  
  
  RESULTS
  All 7 patients recognized the isolated 24-kd kiwi protein as an allergen. The isolated protein consisted of 2 isoforms with isoelectric points of 9.4 and 9.5 migrated as one protein band of 20 kd after SDS-PAGE under nonreducing conditions or at 24 kd under reducing conditions. The partial N-terminal sequence revealed that it is a thaumatin-like protein (TLP) with concanavalin A -binding ability. The protein showed antifungal activity toward Saccharomyces carlsbergensis, and Candida albicans. The protein was degraded by the simulated gastric fluid within 1 minute. Both isoforms bound IgE from a pool of sera in a 2-dimensional PAGE immunoblot. The TLP elicited positive skin prick test responses in 4 (80 %) of 5 patients with OAS.
  
  
  CONCLUSIONS
  This study reported isolation and full characterization of a new kiwi allergen, TLP (isoelectric points of 9.4 and 9.5 and molecular weight of 24 kd), which belongs to the family of pathogenesis-related proteins. The isolated protein expressed antifungal activity toward S carlsbergensis and C albicans.
authors.affiliation: Department of Biochemistry, Faculty of Chemistry, University of Belgrade, Yugoslavia.
authors.forename: Marija
authors.initials: M
authors.lastname: Gavrović-Jankulović
authors.forename: Tanja
authors.initials: T
authors.lastname: ćIrković
authors.forename: Olga
authors.initials: O
authors.lastname: Vucković
authors.forename: Marina
authors.initials: M
authors.lastname: Atanasković-Marković
authors.forename: Arnd
authors.initials: A
authors.lastname: Petersen
authors.forename: Gordana
authors.initials: G
authors.lastname: Gojgić
authors.forename: Lidija
authors.initials: L
authors.lastname: Burazer
authors.forename: Ratko M
authors.initials: RM
authors.lastname: Jankov
mesh_terms: D029042:Actinidia / Q000276:immunology*; D000485:Allergens / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D005512:Food Hypersensitivity / Q000175:diagnosis / Q000276:immunology*; D005638:Fruit / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D007526:Isoelectric Point; D008970:Molecular Weight; D010940:Plant Proteins / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D013549:Sweetening Agents / Q000737:chemistry
chemical_list: D000485:Allergens; D000935:Antifungal Agents; D010940:Plant Proteins; D013549:Sweetening Agents; D007073:Immunoglobulin E; C003427:thaumatin protein, plant