Quantitative analysis of phytate globoids isolated from wheat bran and characterization of their sequential dephosphorylation by wheat phytase.
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 K(m) 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.
Bohn
Lisbeth
L
Department of Agricultural Sciences, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
Josefsen
Lone
L
Meyer
Anne S
AS
Rasmussen
Søren K
SK
D010832:6-Phytase / Q000378:metabolism*; D004043:Dietary Fiber / Q000032:analysis*; D007294:Inositol / Q000378:metabolism; D007700:Kinetics; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010833:Phytic Acid / Q000032:analysis* / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis* / Q000378:metabolism; D014908:Triticum / Q000201:enzymology*
D004043:Dietary Fiber; D010710:Phosphates; D010940:Plant Proteins; D007294:Inositol; D010833:Phytic Acid; D010832:6-Phytase