Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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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)

Phytase was purified from Aspergillus niger culture fluid by molecular sieve filtration on Sephadex G-200, followed by thermal inactivation of acid phosphatase and CM-cellulose chromatography. The 12-fold purified enzyme had two pH optima at 2.7 and 5.5 and was characterized by high thermal stability in alkaline environment and broad substrate specificity. The Michaelis constant of phytase relative to myo-inositol hexaphosphate sodium salt is 4.8 X 10(-4) M and activation energy 9,217 cal/mole. The molecular weight of the enzyme is estimated at 200,000.
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PMID:Some properties of partially purified phytase from Aspergillus niger. 7 23

The changes promoted by germination on phytates, oligosaccharides, crude protein, amino acids and riboflavin contents of black and white cultivars of beans, lentils, chicken-pea and peas, were studied. Seeds germination was carried out in darkness at 25 degrees C and 85% RH during 72 hours, previously soaked overnight in a solution of sodium hypochlorite at a concentration of 50 ppm. Germination capacity was assessed by determining hypocotyl and epicotyl lengths and percent of sprouted seed. The seeds were milled and freeze-dried for the chemical analysis. Germination promoted a significant increase in crude protein content and reduction also significant in phytates levels. These changes were attributed to an increase of proteases and phytase activities. In fact, this enzyme would make a solubilization of phytates and would release soluble protein and minerals. A significant reduction of flatulence oligosaccharides took place, which was also explained by an increase of alpha-galactosidase concentration. Sprouted seeds showed a higher content of almost all amino acid than crude legumes, although this change was variable. Significant increase of riboflavin was also found. Finally, germination decreased ashes and fat contents. These findings were determined in all legumes, although both cultivars of beans showed a higher response to the biochemical changes.
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PMID:[Nutritional changes caused by the germination of legumes commonly eaten in Chile]. 134 62

1. The effect of extrusion cooking of a high-fibre cereal product on digestibility of starch, fibre components and phytate in the stomach and small intestine was studied by in vivo digestion in ileostomy subjects, as well as its effect on ileostomy losses of fat, nitrogen, sodium and potassium. 2. Seven ileostomy subjects were studied during two periods (each of 4 d) while on a constant low-fibre diet supplemented with 54 g/d of a bran-gluten-starch mixture (period A) or the corresponding extruded product (period B). 3. Extrusion cooking, using mild conditions, did not change the content of starch, dietary fibre components or phytate of the bran product, but the phytase (EC 3.1.3.26) activity was lost. During the period using the extruded bran product, there was a significant increase in recovery of phytate-phosphorus (period A, 44% of intake; period B, 73% of intake). The amount of fibre components, fat, fatty acids, N, Na, K, water and the ash weight of the ileostomy contents did not differ between the two periods. Only 0.6 and 0.7% respectively of ingested starch was recovered in ileostomy contents in periods A and B, while the fibre components were almost completely recovered. 4. Extrusion cooking, using even mild conditions, may lead to a considerable impairment in the digestion of phytate, probably due to a qualitative change in phytate and a loss of phytase activity. Starch, before and after extrusion cooking, is almost completely digested in the stomach and small intestine while fibre components are digested to a very small extent.
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PMID:Extrusion cooking of a high-fibre cereal product. 1. Effects on digestibility and absorption of protein, fat, starch, dietary fibre and phytate in the small intestine. 282 63

Soybean phytase (myo-inositol-hexakisphosphate phosphohydrolase; EC 3.1.3.8) was purified from 10-day-old germinating cotyledons using a four-step purification scheme. Phytase was separable from the major acid phosphatase present, and stained as a minor band of the three acid phosphatases detectable by activity staining after gel electrophoresis. The purified enzyme exhibited two closely migrating bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of approximately 59 and 60 KDa. The molar extinction coefficient of the enzyme at 280 nm was estimated to be 7.5 X 10(4) M-1 cm-1. The isoelectric point of phytase, as judged by the elution profile on chromatofocusing, was about 5.5. The enzyme was totally absorbed to a Procion Red HE3B column and eluted as a single protein component at a salt concentration of 250-300 mM. The enzyme possessed a high affinity for phytic acid (apparent Km = 48 microM), and was strongly inhibited by phosphate (apparent Ki = 18 microM), vanadate, and fluoride. Characteristic of other plant phytases, the pH and temperature optima were 4.5-4.8 and 55 degrees C, respectively.
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PMID:Purification and characterization of phytase from cotyledons of germinating soybean seeds. 282 33

Soybean acid phosphatase (orthophosphoric-monoester phosphohydrolase, EC 3.1.3.2) was completely separated from phytase (EC 3.1.3.8) isolated from cotyledons of germinating seeds and purified to homogeneity. A four-step purification regimen consisting of ammonium sulfate fractionation, and ion-exchange, affinity, and chromatofocusing gel chromatographies was employed to achieve a homogeneous preparation. Acid phosphatase activity appeared as a major band of the three forms of acid phosphatase identified on native gels. The purified enzyme had a molecular weight of 53,000 when electrophoresed on 8% sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a molecular weight of 53,000 from its mobility in a Fracto-gel TSK HW-50F gel permeation column. The molar extinction coefficient of the enzyme at 278 nm was estimated to be 4.2 X 10(4) M-1 cm-1. The isoelectric point of the protein, as revealed by chromatofocusing, was about 6.7. The optimal pH for activity, like other plant acid phosphatases, was 5.0. While the enzyme failed to accommodate phytate as a substrate, the enzyme did exhibit a broad substrate selectivity. The affinity of the enzyme for p-nitrophenyl phosphate was high (Km = 70 microM), and activity was competitively inhibited by orthophosphate (Ki = 280 microM). The estimated catalytic turnover number (Kcat) of the enzyme for p-nitrophenyl phosphate was about 430 per second. Although the purified enzyme was stable at 0 degrees C and exhibited maximum catalytic activity at 60 degrees C, thermal inactivation studies indicated that the enzyme lost 100% activity after treatment at 68 degrees C for 10 min.
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PMID:Purification and characterization of acid phosphatase from cotyledons of germinating soybean seeds. 282 34

Purified Aspergillus ficuum phytase's partial primary structure and amino acid and sugar composition were elucidated. Determination of kinetic parameters of the enzyme at different pH values and temperatures indicated no significant alteration of the Km for phytate while the Kcat was affected. The enzyme was able to release more than 51% of the total available Pi from phytate in a 3.0 hr assay at 58 degrees C, but the Kcat dropped to 15% of the initial rate. Substrate selectivity studies revealed phytate to be the preferred substrate. The pH optima of phytase was 5.0, 4.0, and 3.0 for phytate, ATP, and polyphosphate, respectively. The enzyme had varied sensitivity towards cations. While Ca++ and Fe++ produced no effect on the catalytic rate of the enzyme, Cu+, Cu++, Zn++, and Fe were found to be inhibitory. Mn++ was observed to enhance enzyme activity by 33% at 50 microM. Known inhibitors of acid phosphatases e.g. L (+)-tartrate, phosphomycin, and sodium fluoride had no effect on enzyme activity.
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PMID:Aspergillus ficuum phytase: partial primary structure, substrate selectivity, and kinetic characterization. 285 7

Phytic acid is present in many plant systems, constituting about 1 to 5% by weight of many cereals and legumes. Concern about its presence in food arises from evidence that it decreases the bioavailability of many essential minerals by interacting with multivalent cations and/or proteins to form complexes that may be insoluble or otherwise unavailable under physiologic conditions. The precise structure of phytic acid and its salts is still a matter of controversy and lack of a good method of analysis is also a problem. It forms fairly stable chelates with almost all multivalent cations which are insoluble about pH 6 to 7, although pH, type, and concentration of cation have a tremendous influence on their solubility characteristics. In addition, at low pH and low cation concentration, phytate-protein complexes are formed due to direct electrostatic interaction, while at pH > 6 to 7, a ternary phytic acid-mineral-protein complex is formed which dissociates at high Na+ concentrations. These complexes appear to be responsible for the decreased bioavailability of the complexed minerals and are also more resistant to proteolytic digestion at low pH. Development of methods for producing low-phytate food products must take into account the nature and extent of the interactions between phytic acid and other food components. Simple mechanical treatment, such as milling, is useful for those seeds in which phytic acid tends to be localized in specific regions. Enzyme treatment, either directly with phytase or indirectly through the action of microorganisms, such as yeast during breadmaking, is quite effective, provided pH and other environmental conditions are favorable. It is also possible to produce low-phytate products by taking advantage of some specific interactions. For example, adjustment of pH and/or ionic strength so as to dissociate phytate-protein complexes and then using centrifugation or ultrafiltration (UF) has been shown to be useful. Phytic acid can also influence certain functional properties such as pH-solubility profiles of the proteins and the cookability of the seeds.
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PMID:Phytic acid interactions in food systems. 700 70

A simple and rapid method is described for determining the enzymatic activity of microbial phytase. The method is based on the determination of inorganic orthophosphate released on hydrolysis of sodium phytate at pH 5.5.
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PMID:Simple and rapid determination of phytase activity. 801 31

In pursuit of the physiological role of inositol 1,3,4,5-tetrakisphosphate 3-phosphatase, which also attacks inositol pentakisphosphate and inositol hexakisphosphate with much higher affinity (Nogimori, K., Hughes, P.J., Glennon, M.C., Hodgson, M.E., Putney, J.W., Jr., and Shears, S.B. (1991) J. Biol. Chem. 266, 16499-16506), we have studied the subcellular distribution of the enzyme in liver. Initially, we had to overcome the problem that potent endogenous inhibitor(s) compromise the detection of this enzyme in vitro (Hodgson, M.E., and Shears, S.B. (1990) Biochem. J. 267, 831-834). We partially purified these inhibitor(s) by anion-exchange chromatography and gel filtration; inhibitory activity co-eluted with standard inositol hexakisphosphate and was depleted by treatment with phytase. Thus, subcellular fractions were pretreated with phytase before assay of 3-phosphatase activity. Our experiments revealed that the hepatic 3-phosphatase was nearly exclusively restricted to the endoplasmic reticulum, and there was little or no activity in either the cytosol, plasma membranes, mitochondria, or nuclei. Detergent treatment of microsomes indicated that there was 93 +/- 2% latency to mannose-6-phosphatase, an intraorganelle enzyme activity (Vanstapel, F., Pua, K., and Blanckaert, N. (1986) Eur. J. Biochem. 156, 73-77). Similar latencies were found for the hydrolysis of inositol 1,3,4,5-tetrakisphosphate (95 +/- 1%), inositol 1,3,4,5,6-pentakisphosphate (94 +/- 1%), and inositol hexakisphosphate (93 +/- 2%). Treatment of microsomes with either sodium carbonate or phosphatidylcholine-specific phospholipase C, to release luminal contents, led to solubilization of approximately 90% of 3-phosphatase activity. Thus, hepatic 3-phosphatase has a highly restricted access to inositol polyphosphates in vivo that needs to be accounted for in the determination of the physiological role of this enzyme.
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PMID:Hepatic Ins(1,3,4,5)P4 3-phosphatase is compartmentalized inside endoplasmic reticulum. 838 1

Phosphorus (P) is an essential component of many organic and inorganic compounds in vertebrates such as pigs. Therefore, adequate dietary P supply is important to meet daily requirements in order to maintain P homeostasis. Under normal circumstances regulation of P homeostasis occurrs by controlling the absorption rate of inorganic phosphate (Pi) in the upper small intestines and by renal Pi excretion. These processes are mainly mediated by parathyroid hormone (PTH) and calcitriol (1,25-dihydroxycholecalciferol, 1,25-(OH)2D3). If, for example, the Pi level in plasma decreases, renal calcitriol production is stimulated and higher amounts of the hormone are released into the circulation. Calcitriol increases Pi absorption from the intestinal tract by stimulation of a secondary active, sodium-coupled Pi-cotransport system in the upper small intestines. In addition, calcitriol is involved in the mobilization of bone and soft tissue P. Simultaneously, hypercalcemia develops, which can be induced by either increased intestinal Ca absorption and/or Ca mobilization from bone. Hypophosphatemia and hypercalcemia suppress PTH release from the parathyroid glands and thus minimize urinary Pi losses. The concerted action of increased/decreased circulating calcitriol/PTH on the intestinal tract, bone and kidneys normalizes Pi levels in plasma. With respect to adequate P supply in animal nutrition, it must be considered that utilization of dietary P not only depends on absorption capacity of the pig intestinal tract but also on differences in availability of dietary P between ingredients. In feedstuffs of plant origin most of the P is bound as phytate-P and can only be absorbed after enzymatic breakdown of phytic acid by phytases. Intrinsic phytase activity differs between plant materials such as wheat, wheat bran, barley and triticale with higher activities than found in maize and legume seeds subjected to thermal treatments. Supplementation of microbial phytase increased P digestibility more pronounced in those feedstuffs which showed very limited intrinsic phytase activity. At present, a digestibility of about 70% seems to be the upper level for digestibility of P from plant material. From the environmental point of view, an increased digestibility resulting from phytase supplementation offers the possibility to reduce the supplementation of phosphates and the concentration of total P in the diet. Therefore, the amount of P being excreted by the pig can be remarkably reduced. However, the first step for minimizing faecal P excretion should be to supply P in accordance with the animal's requirement.
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PMID:Mechanisms of intestinal phosphorus absorption and availability of dietary phosphorus in pigs. 876 2


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