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Query: EC:3.1.3.8 (phytase)
 1,997 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Escherichia coli pH 2.5 acid phosphatase gene (appA) and three mutants were expressed in Pichia pastoris to assess the effect of strategic mutations or deletion on the enzyme (EcAP) biochemical properties. Mutants A131N/ V134N/D207N/S211N, C200N/D207N/S211N, and A131N/ V134N/C200N/D207N/S211N had four, two, and four additional potential N-glycosylation sites, respectively. Extracellular phytase and acid phosphatase activities were produced by these mutants and the intact enzyme r-AppA. The N-glycosylation level was higher in mutants A131N/V134N/D207N/S211N (48%) and A131N/V134N/ C200N/D207N/S211N (89%) than that in r-AppA (14%). Despite no enhancement of glycosylation, mutant C200N/ D207N/S211N was different from r-AppA in the following properties. First, it was more active at pH 3.5-5.5. Second, it retained more (P < 0.01) phytase activity than that of r-AppA. Third, its specific activity of phytase was 54% higher. Lastly, its apparent catalytic efficiency kcat/Km for either p-nitrophenyl phosphate (5.8 x 10(5) vs 2.0 x 10(5) min(-1) M(-1)) or sodium phytate (6.9 x 10(6) vs 1.1 x 10(6) min(-1) M(-1)) was improved by factors of 1.9- and 5.3-fold, respectively. Based on the recently published E. coli phytase crystal structure, substitution of C200N in mutant C200N/D207N/S211N seems to eliminate the disulfide bond between the G helix and the GH loop in the alpha-domain of the protein. This change may modulate the domain flexibility and thereby the catalytic efficiency and thermostability of the enzyme.
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PMID:Site-directed mutagenesis improves catalytic efficiency and thermostability of Escherichia coli pH 2.5 acid phosphatase/phytase expressed in Pichia pastoris. 1105 Nov 3

A phytate-degrading enzyme was purified approximately 2190-fold from germinated 4-day-old faba bean seedlings to apparent homogeneity with a recovery of 6% referred to the phytase activity in the crude extract. It behaves as a monomeric protein of a molecular mass of approximately 65 kDa. The phytate-degrading enzyme belongs to the acidic phytases. It exhibits a single pH optimum at 5.0. Optimal temperature for the degradation of sodium phytate is 50 degrees C. Kinetic parameters for the hydrolysis of sodium phytate are K(M) = 148 micromol L(-1) and k(cat) = 704 s(-1) at 35 degrees C and pH 5.0. The faba bean phytase exhibits a broad affinity for various phosphorylated compounds and hydrolyzes phytate in a stepwise manner. The first hydrolysis product was identified as D/L-myo-inositol(1,2,3,4,5)pentakisphosphate.
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PMID:Purification and characterization of a phytate-degrading enzyme from germinated faba beans (Vicia faba Var. Alameda). 1136 82

A significant mechanism of arsenate toxicity to Pisum sativum is interference with its mineral nutrient balance. This conclusion is supported by assessments made after exposing P. sativum L. cv. "Phenomen" for 12 days to 12.5, 20.8, and 33.3 mg, and for 32 days to 7.5, 22.1, 36.7, and 73.3 mg of sodium arsenate/kg dry wt soil in the greenhouse. At 20.8 mg of arsenate, mobilization of manganese from the cotyledons was significantly increased and that of zinc decreased. Nitrogen accumulated in the roots. On Day 32, at 22.1 mg of arsenate, magnesium, zinc, and manganese contents of the roots increased, but that of phosphorus of the shoot decreased. The distribution pattern and the ratios between individual elements were severely altered. Relatively more arsenic accumulated from the low than the high soil concentrations. Growth of the shoot was more affected than that of the roots. After a 32-day exposure, chlorophyll content of the leaves increased, but the chlorophyll a/b ratio decreased. On Day 12, at 12.5 mg and 20.8 mg of arsenate, in vivo phytase activity was 64 and 66% that of the controls, respectively.
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PMID:Arsenate toxicity to Pisum sativum: mineral nutrients, chlorophyll content, and phytase activity. 1138 24

Experimental data on phytate phosphorus utilisation by ruminants are scarce. The aim of this study was to estimate the phytase activity of rumen micro-organisms when phytate phosphorus supply is high. A semi-continuous culture system fermentor (RUSITEC) was used. The inoculum was obtained from eight goats fed on either high or low forage level diets. Experimental buffers only differed by the nature of phosphorus monosodium phosphate vs. corn sodium phytate. The nylon bags containing 15 g DM of substrate were removed after a 48-hour incubation period. The system was maintained for 15 days: 5 days for adaptation, in order to obtain a steady state, and 10 days for sampling and recording. No significant differences were observed for DM digestibility, gas production, pH, N-NH3, and SCFA for the different treatments. Bacterial efficiency of phytate phosphorus utilisation was significantly higher (p < 0.001) with organic P, but remained lower than the data usually reported in the literature. These results may be explained by the relative saturation of bacterial phytase activity when the buffer contains a high level of phytate phosphorus.
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PMID:Utilisation of phytate phosphorus by rumen bacteria in a semi-continuous culture system (Rusitec) in lactating goats fed on different forage to concentrate ratios. 1159 23

Bacillus species producing a thermostable phytase was isolated from soil, boiled rice, and mezu (Korean traditinal koji). The activity of phytase increased markedly at the late stationary phase. An extracellular phytase from Bacillus sp. KHU-10 was purified to homogeneity by acetone precipitation and DEAE-Sepharose and phenyl-Sepharose column chromatographies. Its molecular weight was estimated to be 46 kDa on gel filtration and 44 kDa on SDS-polyacrylamide gel elctrophoresis. Its optimum pH and temperature for phytase activity were pH 6.5-8.5 and 40 degrees C without 10 mM CaCl2 and pH 6.0-9.5 and 60 degrees C with 10 mM CaCl2. About 50% of its original activity remained after incubation at 80 degrees C or 10 min in the presence of 10 mM CaCl2. The enzyme activity was fairly stable from pH 6.5 to 10.0. The enzyme had an isoelectric point of 6.8. As for substrate specificity, it was very specific for sodium phytate and showed no activity on other phosphate esters. The Km value for sodium phytate was 50 microM. Its activity was inhibited by EDTA and metal ions such as Ba2+, Cd2+, Co2+, Cr3+, Cu2+, Hg2+, and Mn2+ ions.
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PMID:Purification and properties of extracellular phytase from Bacillus sp. KHU-10. 1159 62

Phytases produced by numerous microorganisms and plants degrade phytic acid that has chelated with metal ions in food and feed. It is important to study phytase for the role of metal ions in nutrition of animals and humans as well as in the reduction of organic phosphate content of aqueous environment. This article reports on solid-state fermentation of phytase from a new substrate of cassava dregs. Large quantities of cassava dregs are produced in tropical areas as a byproduct of cassava starch processing. Protein and inorganic salts were found to be low in cassava dregs. Cassava dregs could be employed for phytase synthesis after the addition of a nitrogen source and mineral salts. Ammonium nitrate was the best nitrogen source among the nitrogen sources investigated, including beef extract, yeast extract, urea, ammonium nitrate, sodium nitrate, and ammonium sulfate. Sodium dodecyl sulfate promoted phytase production from cassava dregs. A maximum phytase yield of 6.73 U/g of dry mass was obtained. The obtained phytase was stable at feed-processing temperature, since 70% of initial enzyme activity was maintained after 30 min of treatment at 75 degrees C.
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PMID:Solid-state fermentation of phytase from cassava dregs. 1196 5

Three phytase (EC 3.1.3.26) isoforms from the roots of 8-d-old maize (Zea mays L. var Consul) seedlings were separated from phosphatases and purified to near homogeneity. The molecular mass of the native protein was 71 kD, and the isoelectric points of the three isoforms were pH 5.0, 4.9, and 4.8. Each of the three isoforms consisted of two subunits with a molecular mass of 38 kD. The temperature and pH optima (40[deg]C, pH 5.0) of these three isoforms, as well as the apparent Michaelis constants for sodium inositol hexakisphosphate (phytate) (43, 25, and 24 [mu]M) as determined by the release of inorganic phosphate, were only slightly different. Phytate concentrations higher than 300 [mu]M were inhibitory to all three isoforms. In contrast, the dephosphorylation of 4-nitrophenyl phosphate was not inhibited by any substrate concentration, but the Michaelis constants for this substrate were considerably higher (137-157 [mu]M). Hydrolysis of phytate by the phytase isoforms is a nonrandom reaction. D/L-Inositol-1,2,3,4,5- pentakisphosphate was identified as the first and D/L-inositol-1,2,5,6-tetrakisphosphate as the second intermediate in phytate hydrolysis. Phytase activity was localized in root slices. Although phosphatase activity was present in the stele and the cortex of the primary root, phytase activity was confined to the endodermis. Phytate was identified as the putative native substrate in maize roots (45 [mu]g P g-1 dry matter). It was readily labeled upon supplying [32P]phosphate to the roots.
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PMID:Maize Root Phytase (Purification, Characterization, and Localization of Enzyme Activity and Its Putative Substrate). 1222 56

Three phytases were purified about 14200-fold (LP11), 16000-fold (LP12), and 13100-fold (LP2) from germinated 4-day-old lupine seedlings to apparent homogeneity with recoveries of 13% (LP11), 8% (LP12), and 9% (LP2) referred to the phytase activity in the crude extract. They behave as monomeric proteins of a molecular mass of about 57 kDa (LP11 and LP12) and 64 kDa (LP2), respectively. The purified proteins belong to the acid phytases. They exhibit a single pH optimum at 5.0. Optimal temperature for the degradation of sodium phytate is 50 degrees C. Kinetic parameters for the hydrolysis of sodium phytate are K(M) = 80 microM (LP11), 300 microM (LP12), and 130 microM (LP2) and k(cat) = 523 s(-1) (LP11), 589 s(-1) (LP12), and 533 s(-1) (LP2) at pH 5.0 and 35 degrees C. The phytases from lupine seeds exhibit a broad affinity for various phosphorylated compounds and hydrolyze phytate in a stepwise manner.
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PMID:Purification and characterization of three phytases from germinated lupine seeds (Lupinus albus var. amiga). 1240 88

Information is needed on organic polyphosphates such as myo-inositol 1,2,3,5/4,6-hexakis dihydrogenphosphate or phytate (IP6) contribution to the sources and sinks of dissolved phosphorus (PO4-P) in the soil-manure-water system. Effects of Na+, Ca2+, Al3+, and Fe3+ and cation to IP6-P mole ratios on the enzymatic dephosphorylation of IP6 were studied to determine controlling mechanisms of dephosphorylation and persistence in manure. Phytate- and PO4-P were analyzed by high-performance liquid chromatography. Phytate dephosphorylation by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8 decreases by 50 +/- 3.6 and 40 +/- 4% at pH 4.5 and 6, respectively, as Ca2+ concentrations increase and cation to IP6-P mole ratios reach 6:6. Polyanionic IP6 has a high affinity for Al3+ and Fe3+ and reductions in dephosphorylation average 27 and 32% at a cation to IP6-P mole ratio of 1:6 for Al3+ and Fe3+, respectively, while reaching more than 99% at a mole ratio of 6:6. A phytase-hydrolyzable phosphorus (PHP) fraction is native to ruminant animal manure and is proportional to total solids (TS) concentration in 1 to 100 g L(-1) suspensions. Added phytase, in effect, increases water-extractable P content of manure and the risk of environmental P dispersion. As the bioavailability and ecological effect of IP6-P appear to be regulated not only by pH-controlled enzyme activity but also by the associated counterions, the differential protective effects of cations influence the accuracy of manure PHP fraction estimates and increase phytate resistance to enzymatic dephosphorylation that may lead to its persistence in manure.
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PMID:Polyvalent cation effects on myo-inositol hexakis dihydrogenphosphate enzymatic dephosphorylation in dairy wastewater. 1270 95

Phosphate utilization by fish is an important issue because of its critical roles in fish growth and aquatic environmental pollution. High dietary phosphorus (P) levels typically decrease the efficiency of P utilization, thereby increasing the amount of P excreted as metabolic waste in effluents emanating from rainbow trout aquaculture. In mammals, vitamin D3 is a known regulator of P utilization but in fish, its regulatory role is unclear. Moreover, the effects of dietary P and vitamin D3 on expression of enzymatic and transport systems potentially involved in phosphate utilization are little known. We therefore monitored production of effluent P, levels of plasma vitamin D3 metabolites, as well as expression of phosphatases and the sodium phosphate cotransporter (NaPi2) in trout fed semipu diets that varied in dietary P and vitamin D3 levels. Mean soluble P concentrations varied markedly with dietary P but not with vitamin D3, and constituted 40-70% of total effluent P production by trout. Particulate P concentrations accounted for 25-50% of effluent P production, but did not vary with dietary P or vitamin D3. P in settleable wastes accounted for <10% of effluent P. The stronger effect of dietary P on effluent P levels is paralleled by its striking effects on phosphatases and NaPi2. The mRNA abundance of the intestinal and renal sodium phosphate transporters increased in fish fed low dietary P; vitamin D3 had no effect. Low-P diets reduced plasma phosphate concentrations. Intracellular phytase activity increased but brushborder alkaline phosphatase activity decreased in the intestine, pyloric caeca, and gills of trout fed diets containing low dietary P. Vitamin D3 had no effect on enzyme activities. Moreover, plasma concentrations of 25-hydroxyvitamin D3 and of 1,25-dihydroxyvitamin D3 were unaffected by dietary P and vitamin D3 levels. The major regulator of P metabolism, and ultimately of levels of P in the effluent from trout culture, is dietary P.
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PMID:Dietary P regulates phosphate transporter expression, phosphatase activity, and effluent P partitioning in trout culture. 1285 80


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