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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)

A study of 35 (5 x 7) male, individually housed, albino rats (initial average weight = 50 g) was undertaken to examine the effect of an addition of microbial phytase to a diet containing phytate on the availability of zinc. The rats were fed a semisynthetic diet based of egg white and cornstarch over a 3-week period. All diets were supplemented with 20 mg Zn/kg. Group I (control) was fed the basal diet free of phytic acid (PA) and phytase. By replacing cornstarch by Na-phytate (0.5% in group II and 1.0% group III), molar phytate: Zn ratios of 25 and 50:1 were obtained, respectively. In groups IV (0.5% PA) and V (1.0% PA) 1000 U of microbial phytase were added. A molar phytate:Zn ratio of 25 (group II) and 50:1 (group III) resulted in a dose-dependent depression of growth and feed efficiency ratio. These negative effects of the addition of PA could be completely counteracted by the supplementation of 1,000 U of phytase in group IV and partially so in group V. Similarly, the apparent absorption and retention of Zn, Zn-concentration in femur and testes and different Zn-status-parameters in plasma (Zn-concentration, percent unsaturated plasma-Zn binding capacity, activity of alkaline phosphatase) were improved by adding 1,000 U microbial phytase/kg diet. The present study shows that an addition of microbial phytase to phytate-rich diets considerably improves the availability of Zn in growing rats.
Z Ernahrungswiss 1992 Dec
PMID:[The effect of a supplement of microbial phytase on zinc availability]. 133 30

To investigate the digestion of phytate in the stomach and small intestine in humans, studies were performed in subjects with established ileostomy. A recently developed high performance liquid chromatography method made it possible to analyze phytate and its degradation products in food and digesta. The digestibility of phytate in raw bran and extruded bran was investigated in seven ileostomy patients. Each subject was studied for two 4-d periods while consuming a constant low fiber diet with the addition of either 54 g/d of a bran-gluten-starch mixture or the corresponding extruded product. During passage through the subject's stomach and small intestine 58%, on average, of the phytate in unprocessed bran was hydrolyzed to inositol penta-, tetra- and triphosphates. When bran was subjected to extrusion cooking, 25% of the inositol hexaphosphate was hydrolyzed to penta- and tetraphosphate and the phytase activity ceased. Essentially no phytate digestion occurred when the ileostomy subjects consumed the extruded product. The reduced digestibility might be due to the lost phytase activity or to formation of indigestible phytate complexes during extrusion cooking.
J Nutr 1987 Dec
PMID:Degradation products of bran phytate formed during digestion in the human small intestine: effect of extrusion cooking on digestibility. 282 27

Due to its high phytate content, the bioavailability of zinc in whole meal cereal products is distinctly lower as compared to foods of animal origin. The effect of reducing the phytate content of cereal products made from rye and wheat on growth, zinc content of femur and blood serum, as well as on the activity of serum alkaline phosphatase was investigated during a 3-week feeding trial in growing rats. The reduction of phytate was achieved by controlling the phytase activity originally present in cereals. By these treatments, the molar phytic acid/zinc ratio in the cereal products was reduced from 27-37 to 3-18. The four parameters under investigation showed a significant improvement in zinc bioavailability with decreasing phytic acid/zinc ratios. The relevance of these results for man and the value of the molar phytic acid/zinc ratio as an indicator of the bioavailability of zinc in foods are discussed.
Z Ernahrungswiss 1987 Dec
PMID:[Biological availability of zinc in whole grain products with different phytate contents]. 343 24

Two types of extracellular acid phosphatases are synthesized by Aspergillus ficuum NRRL 3135: a nonspecific orthophosphoric monoester phosphohydrolase (EC 3.1.3.2) with an optimum pH of 2.0, and an enzyme with restricted specificity, a mesoinositol-hexaphosphate phosphohydrolase (EC 3.1.3.8; phytase) with an optimum pH of 5.5. Although the pH 5.5 enzyme is termed a phytase, both enzymes hydrolyze phytin. Synthesis of the enzymes is repressed by high orthophosphate concentrations in the fermentation medium. The highest total level for each enzyme is synthesized in low orthophosphate medium. In high orthophosphate medium, more pH 5.5 enzyme is produced than pH 2.0 enzyme. In low orthophosphate medium, more pH 5.5 enzyme is produced than pH 2.0 enzyme during the early stages of growth, but the reverse occurs after 5 days. The enzymes are differentiated by heat denaturation at acid and alkaline pH levels. They are separated into two distinct fractions on Sephadex G-100 followed by carboxymethylcellulose column chromatography. This indicates that the two enzymes are structurally different. The K(m) for both enzymes is 1.25 mm when calcium phytate is the substrate. Orthophosphate competitively inhibits the pH 2.0 (K(i) = 1.1 x 10(-2)m) but not the pH 5.5 phosphatase. Neither enzyme is denatured by 50% (w/v) urea or inhibited by 0.01 m tartrate. Thus, they differ from human prostatic phosphatase.
J Bacteriol 1969 Dec
PMID:Regulation of the formation of acid phosphatases by inorganic phosphate in Aspergillus ficuum. 431 67

Phytases are the primary enzymes responsible for the hydrolysis of phytic acid, myo-inositol-1,2,3,4,5,6-hexakisphosphate (I-1,2,3,4,5,6-P6). A number of phytases with varying specificities, properties, and localizations hydrolyze phytic acid present in cells. The specificity of hydrolysis of phytic acid by alkaline phytase from lily (Lilium longiflorum L.) pollen is described. Structures of the intermediate inositol phosphates and the final product were established by a variety of nuclear magnetic resonance techniques (1H-, 31P-, and 31P-1H-detected multiple quantum coherence spectroscopy, and total correlation spectroscopy). On the basis of the structures identified we have proposed a scheme of hydrolysis of phytic acid. Initial hydrolysis of the phosphate ester occurs at the D-5 position of phytic acid to yield the symmetrical I-1,2,3,4,6-P5. The two subsequent dephosphorylations occur adjacent to the D-5 hydroxyl group to yield I-1,2,3-P3 as the final product. Alkaline phytase differs from other phytases in the specificity of hydrolysis of phosphate esters on the inositol ring, its high substrate specificity for phytic acid, and biochemical properties such as susceptibility to activation by calcium and inhibition by fluoride. The physiological significance of alkaline phytase and the biological role of I-1,2,3-P3 remain to be identified.
Plant Physiol 1994 Dec
PMID:Specificity of hydrolysis of phytic acid by alkaline phytase from lily pollen. 784 60

A study with three groups, each with 11 male, individually housed albino rats (initial average weight = 50 g) was undertaken to examine the effect of microbial phytase (added to a diet containing phytate) on the availability of zinc. The rats were fed diets on the basis of soy protein isolate and corn starch over a 3-week period. All diets contained 15-16 mg Zn/kg diet and 0.40% PA. Thus, molar PA:Zn-ratios of 26:1 were obtained. Group I (control) was fed the phytase-free basal diet. In groups II (pair-fed to group I) and III, 1,000 U of microbial phytase (Aspergillus niger var. van tighem) per kg diet were added. Some rats fed the phytase-free basal diet (control) showed typical symptoms of zinc deficiency, including cyclic changes in food intake, anorexia and partial alopecia. By the addition of 1,000 U microbial phytase the apparent absorption of zinc (percent of intake) significantly increased from 33% (control) to 63% (1,000 U, pair-fed) and 66% (1,000 U, ad lib.). Similar positive effects of the phytase-supplementation were observed for three zinc status parameters in plasma, zinc-concentration, percent unsaturated zinc-binding capacity, activity of alkaline phosphatase and the zinc-concentration in femur and testes. The present study shows that an addition of microbial phytase to phytate-rich diets based on soy protein isolate considerably improves the availability of zinc in growing rats.
Z Ernahrungswiss 1993 Dec
PMID:Enhancement of zinc utilization from phytate-rich soy protein isolate by microbial phytase. 812 52

Two experiments were conducted with weanling pigs to determine the effectiveness of a dietary supplement of Aspergillus niger phytase in improving the availability of phytate-P in corn-soybean meal diets without supplemental inorganic P. Experiment 1 consisted of two P and Ca balance trials and two feeding trials. Twelve pigs (8.18 +/- .44 kg BW) were housed individually in stainless steel metabolism cages. Six pigs received 750 phytase units (PU)/g of basal diet and the other six pigs received the basal diet without supplemental phytase as control. In Exp. 2, 96 pigs (8.81 +/- .75 kg BW) were allotted to 16 partially slotted floor pens and their basal diets were supplemented with either 0, 250, 500, or 750 PU/g for 4 wk. Individual pig weights and pen feed consumption were measured weekly. Blood samples were taken from all pigs at the end of each trial in Exp. 1 and from three pigs per pen weekly in Exp. 2 to measure serum (plasma) inorganic P (P) and Ca concentrations and alkaline phosphatase (AP) activities. The results of Exp. 1 indicated that dietary phytase increased P retention by 50% (P < .0001) and decreased fecal P excretion by 42% (P < .0001). Pigs that received dietary phytase had serum P and Ca concentrations and serum AP activities that were nearly normal, whereas control pigs had values indicative of a moderate P deficiency. Favorable effects of phytase disappeared when the phytase was removed from the diet.(ABSTRACT TRUNCATED AT 250 WORDS)
J Anim Sci 1993 Dec
PMID:Supplementing corn-soybean meal diets with microbial phytase linearly improves phytate phosphorus utilization by weanling pigs. 829 88

Two experiments were conducted with crossbred weanling pigs to determine the optimal dietary supplement of Aspergillus niger phytase activity to a low-P, corn-soybean meal basal diet (BD). In Exp. 1, 50 pigs (7.61 +/- .56 kg BW) received the BD supplemented with 750, 1,050, 1,250, or 1,350 phytase units (PU)/g, or .21% P as mono-dibasic calcium phosphate (MDCaP) for 4 wk. In Exp. 2, 12 pigs (6.39 +/- .74 kg BW) were individually housed in metabolism cages and received BD, BD plus the optimal phytase activity (1,200 PU/g), or BD plus .21% P as MDCaP for 2 wk. In Exp. 1, additions of phytase > 1,050 PU/g of BD did not improve ADG, ADFI, gain/feed, or plasma AP activity. Quadratic relationships between dietary phytase activity and these measures were found and their stationary points were at approximately 1,200 PU/g of BD. Estimated maximum responses of these measures in pigs fed phytase were > or = 90% compared with MDCaP. Pigs fed 1,250 PU/g of BD maintained normal plasma P and Ca concentrations. In Exp. 2, pigs that received 1,200 PU/g of BD utilized dietary P more effectively (P < .05) than pigs fed the BD or the BD plus MDCaP. Although they consumed 44% less P per day, these pigs retained only 7% less P than pigs that received MDCaP. One thousand units of phytase activity supported retention of 1.1 mg of P from the BD, and this level of phytase supplementation was equivalent in effect to .91 mg of P from MDCaP.(ABSTRACT TRUNCATED AT 250 WORDS)
J Anim Sci 1993 Dec
PMID:Supplementing corn-soybean meal diets with microbial phytase maximizes phytate phosphorus utilization by weanling pigs. 829 89

In an earlier study a mutant Dictyostelium cell-line (plc-) was constructed in which all phospholipase C activity was disrupted and nonfunctional, yet these cells had nearly normal Ins(1,4,5)P3 levels (Drayer, A.L., Van Der Kaay, J., Mayr, G.W, Van Haastert, P.J.M. (1990) EMBO J. 13, 1601-1609). We have now investigated if these cells have a phospholipase C-independent de novo pathway of Ins(1,4,5)P3 synthesis. We found that homogenates of plc- cells produce Ins(1,4,5)P3 from endogenous precursors. The enzyme activities that performed these reactions were located in the particulate cell fraction, whereas the endogenous substrate was soluble and could be degraded by phytase. We tested various potential inositol polyphosphate precursors and found that the most efficient were Ins(1,3,4,5,6)P5, Ins(1,3,4,5)P4, and Ins(1,4,5,6)P4. The utilization of Ins(1,3,4,5,6)P5, which can be formed independently of phospholipase C by direct phosphorylation of inositol (Stephens, L.R. and Irvine, R.F. (1990) Nature 346, 580-582), provides Dictyostelium with an alternative and novel pathway of de novo Ins(1,4,5)P3 synthesis. We further discovered that Ins(1,3,4,5,6)P5 was converted to Ins(1,4,5)P3 via both Ins(1,3,4,5)P4 and Ins(1,4,5,6)P4. In the absence of calcium no Ins(1,4,5)P3 formation could be observed; half-maximal activity was observed at low micromolar calcium concentrations. These reaction steps could also be performed by a single enzyme purified from rat liver, namely, the multiple inositol polyphosphate phosphatase. These data indicate that organisms as diverse as rat and Dictyostelium possess enzyme activities capable of synthesizing the second messengers Ins(1,4,5)P3 and Ins(1,3,4,5)P4 via a novel phospholipase C-independent pathway.
J Biol Chem 1995 Dec 15
PMID:A novel, phospholipase C-independent pathway of inositol 1,4,5-trisphosphate formation in Dictyostelium and rat liver. 853 Mar 62

Phytase from Aspergillus niger increases the availability of phosphorus from feed for monogastric animals by releasing phosphate from the substrate phytic acid. A phytase cDNA was constitutively expressed in transgenic tobacco (Nicotiana tabacum) plants. Secretion of the protein to the extracellular fluid was established by use of the signal sequence from the tobacco pathogen-related protein S. The specific phytase activity in isolated extracellular fluid was found to be approximately 90-fold higher than in total leaf extract, showing that the enzyme was secreted. This was confirmed by use of immunolocalization. Despite differences in glycosylation, specific activities of tobacco and Aspergillus phytase were identical. Phytase was found to be biologically active and to accumulate in leaves up to 14.4% of total soluble protein during plant maturation. Comparison of phytase accumulation and relative mRNA levels showed that phytase stably accumulated in transgenic leaves during plant growth.
Plant Physiol 1995 Dec
PMID:Stable accumulation of Aspergillus niger phytase in transgenic tobacco leaves. 853 88


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