Phytase

Cereals contain about 1% of phytate [myoinositol (1,2,3,4,5,6) hexakisphosphate], which binds about 70% of the phosphorus in the grain. Since it occurs mainly in the aleurone layer, the content of phytate in flour depends on the extent of grinding (Table 15.20). A part of it is hydrolyzed in stages to myo-inositol during dough making. 

The phytases originate in cereals (Table 15.21), but are also synthesized by microorganisms, e. g., yeast. Therefore, if the baking process 

Type of Phytase Phytate cereal activity content  

Partial hydolysis of phytate to myo-inositoltetrakis- and -triphosphate is desirable from a nutritional physiological point of view. In comparison with phytate, these less phosphory-lated myo-inositols do not form such stable complexes with cations. Consequently, the absorption of zinc, iron, calcium and magnesium ions is not 

The involvement of endogenous lipoxygenase in the baking of wheat flour is not clear. However, by addition of lipoxygenase-active soy flour, a significant improvement of the flour quality is achieved (cf. 15.4.1.4.3). 

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Malted barley contains a- and P-amylases along with proteases and phytases. Most standardi2ed microbial en2yme preparations for industrial starch conversion contain approximately 100 times more amylase activity than malt. In beermaking, malt is not just valuable for its en2ymes but also for flavor compounds. 

BOLING-FRANKENBACH S D, PETER 0 M, DOUGLAS M W, SNOW J L, PARSONS C M, BAKER D H (2001) Efficacy of phytase for increasing protein efficiency ratio values of feed ingredients. Poult Sci. 80 1578-84. 

RAPP c, LANTZSCH H J, DROCHNER w (2001) Hydrolysis of ph)dic acid hy intrinsic plant and supplemented microbial phytase Aspergillus niger) in the stomach and small intestine of minipigs fitted with re-entrant cannnlas. 3. Hydrolysis of ph)dic acid (1P6) and occurrence of hydrolysis products (1P5,1P4, 1P3 and 1P2). JAnim Physiol Anim Nutr (Berl). 85 420-30. 

Myo-inositol is one of the most biologically active forms of inositol. It exists in several isomeric forms, the most common being the constituent of phospholipids in biological cell membranes. It also occurs as free inositol and as inositol hexaphosphate (IP6) also known as phytate which is a major source from food. Rice bran is one of the richest sources of IP6 as well as free inositol. Inositol is considered to belong to the B-complex vitamins. It is released in the gastrointestinal tract of humans and animals by the dephosphorylation of IP6 (phytate) by the intestinal enzyme phytase. Phytase also releases intermediate products as inositol triphosphate and inositol pentaphosphate. Inositol triphosphate in cellular membrane functions as an important intra- and intercellular messenger, that merits its value as a nutritional therapy for cancer. 

Defatted soy flour was suspended in water to 8% (v/w) protein, pH was adjusted to 6 by HCl before 640 mg/L Novozyme 415 (a-galactosidase), 10 mg/L Phytase L (Novo Nordisk) and 53 mg enzyme protein/L rhamnogalacturonase B were added. After 4 hours at 50 C the pH was adjusted to 8 by NaOH, and the slurry was centrifuged. The supernatant was pasteurized (85°C, 5 minutes) and freezedried. Protein was measured as 6.25 x Kjeldahl N. Phytate was measured as described in [16], and dietary fibres were analysed as described in [17]. 

The ability of RGase B to solubilise soy fibres is useful for the production of a fibre enriched dietetic soy product. Soy milk has the disadvantages that it has a low fibre content and a high content of phytate and of stachyose and raffinose. To overcome these disadvantages a-galactosidase was used to reduce the amount of stachyose and raffinose, phytase to degrade the phytate, and RGase B to release fibre material. 

Phytic acid (inisitol hexakisphosphate) is the main storage form of phosphorus in plants. The phosphorus is not bioavailable to non-ruminants as they lack the enzymes to break it down. Novozyme has developed a commercial enzyme, phytase, that can be added to animal feed to release the phosphorus. No inorganic phosphorus needs to be added. This shift in the source of phosphorous has a large impact on the environmental footprint of pig farming. 

The annual impact of shifting all the pig herd in Denmark to a phytase supplemented diet instead of MCP supplemented would be a reduction in greenhouse gases by 27 kT CO2 equivalent, reduction in acidification by 450 T SO2 equivalent, reduction in nutrient enrichment by 1200 T phosphate equivalent, and avoiding mining of 20 kT phosphate bearing rock. 

M. Li, M. Osaki, I. M. Rao, and T. Tadano, Secretion of phytase from the roots of several plant species under phosphoru.s-dcficient conditions. Plant Soil 795 161 (1997). 

L. BeiBner and W. Romer, Improving the availability of phytate-phosphorus to sugar beet (Beta vulgaris L.) by phytase application to soil, 9th International Kollo-c/uiuin for the Optimization of Plant Nutrition, Prague, Czech Republic, 1996. p. 327. 

G. R. Findenegg and J. A. Nelenians, The effect of phytase on the availability of P from myo-inositol hexaphosphate (phytate) for maize root. Plant Soil 754 189 (1993). 

Guoa, M., Hang, H. and Zhua, T. (2008) Effect of glycosylation on biochemical characterization of recombinant phytase expressed in Pichia pastoris. Enzyme and Microbial Technology, 42, 340-345. 

Mayer, A.F., Hellmuth, K., Schlieker, H. et al. (1999) An expression system matures a highly efficient and cost-effective process for phytase production by recombinant strains of Hansenulapolymorpha. Biotechnology and Bioengineering, 63 (3), 373-381. 

Viveros A, Centeno C, Brenes A, Canales R and Lozano A (2000), Phytase and acid phosphatase in plant feedstuffs , J Agric Food Chem, 48, 4009-4013. 

Andriotis, V. M. E. and Ross, J. D. (2003). Isolation and characterisation of phytase from dormant Corylus avellana seeds. Phytochemistry 64 689-699. 

As discussed above, wheat has been used only rarely for molecular farming. Thus far, the only example of a pharmaceutical protein produced in wheat is a single chain Fv antibody, which was expressed using the Ubil promoter and achieved a maximum expression level of 1.5 pg g 1 dry weight [77]. Transgenic wheat producing Aspergillus phytase has also been reported [78]. 

Both lipases and lipoxygenases are present in the bran and the germ. Phytases are nutritionally important as they liberate the phosphorus, of which approximately 70% is in the kernel bound to phytin. Phytin blocks the intestinal absorption of both iron and calcium. Phytase is also present in yeast, which is why leavened bread is nutritionally superior to unleavened bread. There have been concerns about the incidence of rickets among those of South Asian origin who eat chapattis, live in the UK, and have a tendency to keep their skin covered up from the sun. 

Without considering the aomplexity of additional interactions of phytate and Ca2+ with other polyvalent cations, proteins, and fiber, Figures 3 and 4 predict that the progressive elimination of bran in Table II lowers the concentration of soluble Ca2+. This effect is especially pronounced in the bread, where part of the remaining phytate was hydrolyzed by yeast phytase during leavening (Table II). These conclusions and their implications... 

The diet treatments were level of phytate intake, either 0.2 or 2.0 g/day. Each level was consumed for 15 days, three consecutive repeats of the 5-day menu cycle. To provide 2.0 g/day of phytic acid, 36 g of wheat bran was baked into 6 muffins and two muffins were eaten each meal. Dephytinized bran was prepared by incubating the bran in water and allowing the endogenous phytase to hydrolyze the phytate, then the entire incubation mixture was freeze-dried (4) and 36 g baked into 6 muffins. Thus, the intake of all nutrients and neutral detergent fiber was the same for both phytate intakes. Five subjects consumed the whole bran muffins for 15 days followed by the dephytinized bran muffins for 15 days and the other 5 subjects in the reverse order. Brilliant blue dye was given at breakfast on the first day of each collection period to aid in demarcation of stools. Stool composites were made for days 1-5, 6-15, 16-20 and 21-30 and urine composites for days 6-15, and 21-30. Daily food composites were made, homogenized, freeze-dried and then analyzed to determine mineral nutrient intakes. 

Phosphorylation glycerol is phosphorylated with pyrophosphate by phytase at pH 4.0, 37 °C. Racemic glycerol-3-phosphate is obtained in 100% yield (based on pyrophosphate) in 95% glycerol after 24 h. 

Oxidation by raising the pH (to 7.5) phytase activity is switched off hydrolysis is prevented. Oxidation of L-glycerol-3-phosphate to DHAP by GPO at 55% glycerol (v/v) is quantitative. Catalase is added to suppress the build-up of hydrogen peroxide. The D-isomer is converted back into glycerol and phosphate in the last step. 

Dephosphorylation lowering the pH back to 4 switches on phytase s activity ... 

This enzyme [EC 3.1.3.26], also known as phytase, phy-tate 6-phosphatase, and myo-inositol-hexaphosphate 6-phosphohydrolase, catalyzes the hydrolysis of myoinositol hexakisphosphate to produce 1-myo-inositol... 

NAD(P)H DEHYDROGENASE (QUINONE) PHYSICAL ORGANIC CHEMISTRY TERMINOLOGY (lUPAC Recommendations) 6-PHYTASE... 

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