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)

Phytases catalyse the hydrolysis of phytate (myo-inositol hexakisphosphate) to myo-inositol and inorganic phosphate. In this study genes encoding novel phytases from two different filamentous fungi, Aspergillus terreus strain 9A-1 and Myceliophthora thermophila were isolated. The encoded PhyA phytase proteins show 60% (A. terreus) and 48% (M. thermophila) identity, respectively, to the PhyA of Aspergillus niger and have 21-29% identity compared to other histidine acid phosphatases. All three PhyA proteins, in contrast to the A. niger pH 2.5-optimum acid phosphatase, prefer phytic acid as substrate and show enzyme activity at a broad range of acidic pH values. Based on their enzyme characteristics and protein sequence homology, the phytases form a novel subclass of the histidine acid phosphatase family.
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PMID:The phytase subfamily of histidine acid phosphatases: isolation of genes for two novel phytases from the fungi Aspergillus terreus and Myceliophthora thermophila. 902 98

The characterization of the multiple inositol polyphosphate phosphatase (MIPP) is fundamental to our understanding of how cells control the signalling activities of 'higher' inositol polyphosphates. We now describe our isolation of a 2.3 kb cDNA clone of a rat hepatic form of MIPP. The predicted amino acid sequence of MIPP includes an 18 amino acid region that aligned with approximately 60% identity with the catalytic domain of a fungal inositol hexakisphosphate phosphatase (phytase A); the similarity encompassed conservation of the RHGXRXP signature of the histidine acid phosphatase family. A histidine-tagged, truncated form of MIPP was expressed in Escherichia coli and the enzymic specificity of the recombinant protein was characterized: Ins(1,3,4,5,6)P5 was hydrolysed, first to Ins(1,4,5,6)P4 and then to Ins(1,4,5)P3, by consecutive 3- and 6-phosphatase activities. Inositol hexakisphosphate was catabolized without specificity towards a particular phosphate group, but in contrast, MIPP only removed the beta-phosphate from the 5-diphosphate group of diphosphoinositol pentakisphosphate. These data, which are consistent with the substrate specificities of native (but not homogeneous) MIPP isolated from rat liver, provide the first demonstration that a single enzyme is responsible for this diverse range of specific catalytic activities. A 2.5 kb transcript of MIPP mRNA was present in all rat tissues that were examined, but was most highly expressed in kidney and liver. The predicted C-terminus of MIPP is comprised of the tetrapeptide SDEL, which is considered a signal for retaining soluble proteins in the lumen of the endoplasmic reticulum; the presence of this sequence provides a molecular explanation for our earlier biochemical demonstration that the endoplasmic reticulum contains substantial MIPP activity [Ali, Craxton and Shears (1993) J. Biol. Chem. 268, 6161-6167].
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PMID:Molecular cloning and expression of a rat hepatic multiple inositol polyphosphate phosphatase. 935 36

A close examination of the protein sequence encoded by the Arabidopsis thaliana gene F21M12.26 reveals the gene product to be a phosphomonoesterase, acid optimum (EC 3.1.3.2). A subclass of this broad acid phosphatase is also known as 'histidine acid phosphatase. ' This is the first sequence-based evidence for a 'histidine acid phosphatase' in a dicotyledon. One important member of this class of enzymes is Aspergillus niger (ficuum) phytase, which came into prominence for its commercial application as a feed additive. The putative protein from A. thaliana gene F21M12.26 shares many important features of Aspergillus phytase, namely, size, active-site sequence, catalytic dipeptide and ten cysteine residues located in the key areas of the molecule, but lacks all nine N-glycosylation sites.
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PMID:Identification of a histidine acid phosphatase (phyA)-like gene in Arabidopsis thaliana. 979 Sep 41

Phytases catalyze the hydrolysis of phytate and are able to improve the nutritional quality of phytate-rich diets. Escherichia coli phytase, a member of the histidine acid phosphatase family has the highest specific activity of all phytases characterized. The crystal structure of E. coli phytase has been determined by a two-wavelength anomalous diffraction method using the exceptionally strong anomalous scattering of tungsten. Despite a lack of sequence similarity, the structure closely resembles the overall fold of other histidine acid phosphatases. The structure of E. coli phytase in complex with phytate, the preferred substrate, reveals the binding mode and substrate recognition. The binding is also accompanied by conformational changes which suggest that substrate binding enhances catalysis by increasing the acidity of the general acid.
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PMID:Crystal structures of Escherichia coli phytase and its complex with phytate. 1065 11

Phytases are a special class of phosphatase that catalyze the sequential hydrolysis of phytate to less-phosphorylated myo-inositol derivatives and inorganic phosphate. Phytases are added to animal feedstuff to reduce phosphate pollution in the environment, since monogastric animals such as pigs, poultry, and fish are unable to metabolize phytate. Based on biochemical properties and amino acid sequence alignment, phytases can be categorized into two major classes, the histidine acid phytases and the alkaline phytases. The histidine acid phosphatase class shows broad substrate specificity and hydrolyzes metal-free phytate at the acidic pH range and produces myo-inositol monophosphate as the final product. In contrast, the alkaline phytase class exhibits strict substrate specificity for the calcium-phytate complex and produces myo-inositol trisphosphate as the final product. This review describes recent findings that present novel viewpoints concerning the molecular basis of phytase classification.
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PMID:Biochemical properties and substrate specificities of alkaline and histidine acid phytases. 1458 76

The gene phyA encoding phytase was isolated from Obesumbacterium proteus genomic library and sequenced. The cleavage site of the PhyA signal peptide was predicted and experimentally proved. The PhyA protein shows maximum identity of 53% and 47% to phosphoanhydride phosphorylase from Yersinia pestis and phytase AppA from Escherichia coli, respectively. Based on protein sequence similarity of PhyA and its homologs, the phytases form a novel subclass of the histidine acid phosphatase family. To characterize properties of the PhyA protein, we expressed the phyA gene in E. coli. The specific activity of the purified recombinant PhyA was 310 U mg(-1) of protein. Recombinant PhyA showed activity at pH values from 1.5 through 6.5 with the optimum at 4.9. The temperature optimum was 40-45 degrees C at pH 4.9. The Km value for sodium phytate was 0.34 mM with a Vmax of 435 U mg(-1).
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PMID:Gene cloning, expression and characterization of novel phytase from Obesumbacterium proteus. 1525 Dec 9

A novel phytase gene appA, with upstream and downstream sequences from Citrobacter amalonaticus CGMCC 1696, was cloned by degenerate polymerase chain reaction (PCR), and thermal asymmetric interlaced (TAIL) PCR and was overexpressed in Pichia pastoris. Sequence analysis revealed one open reading frame that consisted of 1311 bp encoding a 436-amino-acid protein, which had a deduced molecular mass of 46.3 kDa. The phytase appA belongs to the histidine acid phosphatase family and exhibits the highest identity (70.1%) with C. braakii phytase. The gene was overexpressed in P. pastoris. The secretion yield of recombinant appA protein was accumulated to approximately 4.2 mg.mL(-1), and the enzyme activity level reached 15,000 U x mL(-1), which is higher than any previous reports. r-appA was glycosylated, as shown by Endo H treatment. r-appA was purified and characterized. The specific activity of r-appA for sodium phytate was 3548 U.mg(-1). The optimum pH and temperature for enzyme activity were 4.5 and 55 degrees C, respectively. r-appA was highly resistant to pepsin or trypsin treatment. This enzyme could be an economic and efficient alternative to the phytases currently used in the feed industry.
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PMID:A novel phytase appA from Citrobacter amalonaticus CGMCC 1696: gene cloning and overexpression in Pichia pastoris. 1765 39

Two novel phytase genes belonging to the histidine acid phosphatase family were cloned from Yersinia rohdei and Y. pestis and expressed in Pichia pastoris. Both the recombinant phytases had high activity at pH 1.5-6.0 (optimum pH 4.5) with an optimum temperature of 55 degrees C. Compared with the major commercial phytases from Aspergillus niger, Escherichia coli, and a potential commercial phytase from Y. intermedia, the Y. rohdei phytase was more resistant to pepsin, retained more activity under gastric conditions, and released more inorganic phosphorus (two to ten times) from soybean meal under simulated gastric conditions. These superior properties suggest that the Y. rohdei phytase is an attractive additive to animal feed. Our study indicated that, in order to better hydrolyze the phytate and release more inorganic phosphorus in the gastric passage, phytase should have high activity and stability, simultaneously, at low pH and high protease concentration.
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PMID:A novel phytase from Yersinia rohdei with high phytate hydrolysis activity under low pH and strong pepsin conditions. 1854 46

The role of disulfide bridges in the folding of Aspergillus niger phytase pH 2.5-optimum (PhyB) was investigated using dynamic light scattering (DLS). Guanidinium chloride (GuCl) at 1.0 M unfolded phytase; however, its removal by dialysis refolded the protein. The thiol reagent tris(2-carboxyethyl)phosphine (TCEP) reduces the refolding activity by 68%. The hydrodynamic radius (R(H)) of PhyB phytase decreased from 5.5 to 4.14 nm when the protein was subjected to 1.0 M GuCl concentration. The active homodimer, 183 kDa, was reduced to a 92 kDa monomer. The DLS data taken together with activity measurements could indicate whether refolding took place or not in PhyB phytase. The correlation between molecular mass and the state of unfolding and refolding is a very strong one in fungal phytase belonging to histidine acid phosphatase (HAP). Unlike PhyA phytase, for which sodium chloride treatment boosted the activity at 0.5 M salt concentration, PhyB phytase activity was severely inhibited under identical condition. Thus, PhyA and PhyB phytases are structurally very different, and their chemical environment in the active site and substrate-binding domain may be different to elicit such an opposite reaction to monovalent cations.
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PMID:Unfolding and refolding of Aspergillus niger PhyB phytase: role of disulfide bridges. 1868 44

A new phytase (APPA) with optimum pH 2.5--substantially lower than that of most of microbial phytases (pH 4.5-6.0)--was cloned from Yersinia frederiksenii and heterologously expressed in Escherichia coli. Containing the highly conserved motifs typical of histidine acid phosphatases, APPA has the highest identity (84%) to the Yersinia intermedia phytase (optimal pH 4.5), a member of histidine acid phosphatase family. Based on sequence alignment and molecular modeling of APPA and related phytases, APPA has only one divergent residue, Ser51, in close proximity to the catalytic site. To understand the acidic adaptation of APPA, five mutants (S51A, S51T, S51D, S51K, and S51I) were constructed by site-directed mutagenesis, expressed in E. coli, purified, and characterized. Mutants S51T and S51I exhibited a shift in the optimal pH from 2.5 to 4.5 and 5.0, respectively, confirming the role of Ser51 in defining the optimal pH. Thus, a previously unrecognized factor other than electrostatics--presumably the side-chain structure near the active site--contributes to the optimal pH for APPA activity. Compared with wild-type APPA, mutant S51T showed higher specific activity, greater activity over pH 2.0-5.5, and increased thermal and acid stability. These properties make S51T a better candidate than the wild-type APPA for use in animal feed.
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PMID:Improvement of Yersinia frederiksenii phytase performance by a single amino acid substitution. 1937 62


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