Wheat inositol phosphates

Brearley, C.A., and Hanke, D.E., 1996b, Inositol phosphates in barley (Hordeum vulgare L.) aleurone tissue are sterochemically similar to the products of breakdown of Ins P6 in vitro by wheat bran phytase. Biochem. J. 318 279-286. 

Eim, P.E. andTate, M.E. (1 973)The phytases. III. Properties of phytase fractions F, and from wheat bran and the m/o-inositol phosphates produced by fraction F. Biochimica et Biophysica Acta 302, 315-328. 

In wheat, the element P is present as Ca and Mg salts of phytic acid, KH2PO4, B vitamins and relatively minor quantities of phospholipids and nucleic acids. Some typical phytic acid contents are indicated in Table 12.23. In bran and nnts most of the P is present as phytic acid salts. Although phytates (inositol phosphates) are believed to have some nutrient value, they form complexes with essential trace metals such as Zn and Fe making them less available for nutritional purposes [57]. 

The catabolites of phytase activity in wheat are myo-inositol, phosphate, and the macroelements potassium, magnesium and calcium. Myo-inositol phosphate ester intermediates with fewer than six phosphate groups do not accumulate within the grain during hydrolysis of the phytin molecule [94], which is indicative of its rapid and complete breakdown by phytases. Movement of the catabolites from the aleurone layer and their redistribution into the developing seedling appears to be by simple diffusion through the endosperm, without any apparent competition for uptake by the scutellum. 

Inositol Monophosphate, myo-lnosilol 1-(if(hydrogen phosphate). C4HuOjP mol wt 260.14. C 27.70%, H 5.04%, O 55.35%, P 11.91%. Prepd by enzymatic hydrolysis of sodium phytate using the phy tase of wheat bran Poster -nak, Posternak, Helv. Chim. Acta 12, 1165 (1929) McCormick, Carter, Biochem. Prepn. 2, 65 (1952). 

Activation energy values for the hydrolysis of myo-inositol hexakisphosphate and of esters with lower phosphate content were between 35.6 kJ/mol in germinated Phaseolus aureus (Mandal et al., 1972) and 50.2 kJ/mol in wheat bran (Nagai and Funahashi, 1962). The optimum temperature for the enzymatic hydrolysis of myo-inositol hexakisphosphate varies among phytases between 45 and 57°C (Nayini and Markakis, 1986), and even up to 60°C for the phytase of Bacillus subtilis (Powar and Jagannathan, 1982). 

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