Quantitative analysis of phytate globoids isolated from wheat bran and characterization of their sequential dephosphorylation by wheat phytase

Lisbeth Bohn, Lone Josefsen, Anne S. Meyer, S.K. Rasmussent

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Abstract

Wheat phytase was purified to investigate the action of the enzyme toward its pure substrate (phytic acid - myo-inositol hexakisphosphate) and its naturally occurring substrate (phytate globoids). Phytate globoids were purified to homogeneity from wheat bran, and their nutritionally relevant parameters were quantified by ICP-MS. The main components of the globoids were phytic acid (40% w/w), protein (46% w/w), and several minerals, in particular, K > Mg > Ca > Fe (in concentration order). Investigation of enzyme kinetics revealed that Km and V-max decreased by 29 and 37%, respectively, when pure phytic acid was replaced with phytate globoids as substrate. Time course degradation of phytic acid or phytate globoids using purified wheat phytase was followed by HPIC identification of inositol phosphates appearing and disappearing as products. In both cases, enzymatic degradation initiated at both the 3- and 6-positions of phytic acid and end products were inositol and phosphate.
Original languageEnglish
JournalJournal of Agricultural and Food Chemistry
Volume55
Issue number18
Pages (from-to)7547-7552
ISSN0021-8561
DOIs
Publication statusPublished - 2007

Keywords

  • Triticum aestivum
  • phytate globoids
  • inositol phosphates
  • kinetics
  • minerals
  • wheat bran
  • wheat phytase

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