P39, a novel soybean protein allergen, belongs to a plant-specific protein family and is present in protein storage vacuoles

Ping Xiang, Lisa M. Baird, Rudolf Jung, Michael G. Zeece, John Markwell, Gautam Sarath

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Soybean lecithins are seeing increasing use in industry as an emulsifier and food additive. They are also a growing source of human food allergies, which arise principally from the proteins fractionating with the lecithin fraction during manufacture. A previous study (Gu, X.; Beardslee, T.; Zeece, M.; Sarath, G.; Markwwell, J. Int Arch. Allergy Immunol. 2001, 126, 218-225) identified several allergenic proteins in soybean lecithins and a soybean IgE-binding protein termed P39 was discovered. However, very little was known about this protein except that it was coded by the soybean genome. This paper investigates key biological and immunological properties of this potential soybean lecithin allergen. P39 is encoded by a multigene family in soybeans and in several other higher plants. The soybean P39-1 protein and its essentially indistinguishable homologue, P39-2, have been cloned and studied. These proteins and their homologues belong to a family of plant-specific proteins of unknown function. In soybeans, P39-1 is seed specific, and its transcript levels are highest in developing seeds and decline during seed maturation. In contrast, P39 protein was detectable only in the fully mature, dry seed. Subcellular fractionation revealed that P39 protein was strongly associated with oil bodies; however, immunolocalization indicated P39 was distributed in the matrix of the protein storage vacuoles, suggesting that association with oil bodies was an artifact arising from the extraction procedure. By the use of recombinant techniques it has also been documented that IgE-binding epitopes are present on several different portions of the P39-1 polypeptide.

Original languageEnglish (US)
Pages (from-to)2266-2272
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Issue number6
StatePublished - Mar 26 2008
Externally publishedYes


  • Allergen
  • Oil bodies
  • P39
  • Plant-specific protein family
  • Protein
  • Protein storage vacuoles
  • Soybean lecithin

ASJC Scopus subject areas

  • General Chemistry
  • General Agricultural and Biological Sciences


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