Phosphorus metabolism in the coral–zooxanthellae symbiosis: characterization and possible roles of two acid phosphatases in the algal symbiont Symbiodinium sp

1989 ◽  
Vol 238 (1291) ◽  
pp. 193-202 ◽  
Keyword(s):  
Inorganic Phosphate ◽  
Physiological Role ◽  
Phosphate Esters ◽  
Phosphorus Metabolism ◽  
Acid Phosphatases ◽  
Hard Coral ◽  
Algal Symbiont ◽  
Acropora Formosa ◽  
Hydrolysis Of

Cell-free extracts of zooxanthellae ( Symbiodinium sp.) from the hard coral Acropora formosa contained two acid phosphatases that were resolved by affinity chromatography on concanavalin-A-Sepharose. The enzymes had similar properties, with the exception that phosphatase P-1 hydrolysed polyphosphate and pyrophosphate, whereas phosphatase P-2 had no activity towards either. The high activity of phosphatase P-1 with polyphosphate implies that the physiological role of this enzyme may be the mobilization of this phosphate storage compound. The physiological substrate of phosphatase P-2 is unknown, but the most likely role of this enzyme is the hydrolysis of phosphate esters exterior to the plasmalemma, before uptake of the released inorganic phosphate by the algal transport system. Cultured zooxanthellae ( S. kawagutii ) contained phosphatase P-2 only; the significance of this difference is unknown. The activities of P-1 and P-2 were always high in freshly isolated zooxanthellae, and both activities were repressed after incubation in phosphate-supplemented media. The implication is therefore that the algae in the coral-zooxanthellae symbiosis may be phosphate limited.

The role of acid phosphatases in plant phosphorus metabolism

1994 ◽  
Vol 90 (4) ◽  
pp. 791-800 ◽  
Author(s):  
Stephen M. G. Duff ◽  
Gautam Sarath ◽  
William C. Plaxton
Keyword(s):  
Phosphorus Metabolism ◽  
Acid Phosphatases

The role of acid phosphatases in plant phosphorus metabolism

1994 ◽  
Vol 90 (4) ◽  
pp. 791-800 ◽  
Author(s):  
Stephen M. G. Duff ◽  
Gautam Sarath ◽  
William C. Plaxton
Keyword(s):  
Phosphorus Metabolism ◽  
Acid Phosphatases

scholarly journals Genetic Characterization of a Cell Envelope-Associated Proteinase from Lactobacillus helveticus CNRZ32

1999 ◽  
Vol 181 (15) ◽  
pp. 4592-4597 ◽  
Author(s):  
Jeffrey A. Pederson ◽  
Gerald J. Mileski ◽  
Bart C. Weimer ◽  
James L. Steele
Keyword(s):  
Cell Surface ◽  
Deletion Mutant ◽  
Cell Envelope ◽  
Physiological Role ◽  
Lactobacillus Helveticus ◽  
Whole Cells ◽  
A Cell ◽  
Hydrolysis Of

ABSTRACT A cell envelope-associated proteinase gene (prtH) was identified in Lactobacillus helveticus CNRZ32. TheprtH gene encodes a protein of 1,849 amino acids and with a predicted molecular mass of 204 kDa. The deduced amino acid sequence of the prtH product has significant identity (45%) to that of the lactococcal PrtP proteinases. Southern blot analysis indicates thatprtH is not broadly distributed within L. helveticus. A prtH deletion mutant of CNRZ32 was constructed to evaluate the physiological role of PrtH. PrtH is not required for rapid growth or fast acid production in milk by CNRZ32. Cell surface proteinase activity and specificity were determined by hydrolysis of αs1-casein fragment 1-23 by whole cells. A comparison of CNRZ32 and its prtH deletion mutant indicates that CNRZ32 has at least two cell surface proteinases that differ in substrate specificity.

scholarly journals The substrate specificity of acid α-glucosidase from rabbit muscle

1971 ◽  
Vol 124 (4) ◽  
pp. 701-711 ◽  
Author(s):  
T. N. Palmer
Keyword(s):  
Substrate Inhibition ◽  
Physiological Role ◽  
Liver Glycogen ◽  
Rabbit Muscle ◽  
Ph Optimum ◽  
Enzyme Action ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Hydrolysis Of

1. Acid α-glucosidase was purified 3500-fold from rabbit muscle. 2. The enzyme was activated by cations, the degree of activation varying with the substrate. Enzyme action on glycogen was most strongly activated and activation was apparently of a non-competitive type. With rabbit liver glycogen as substrate, the relative Vmax. increased 15-fold, accompanied by an increase in Km from 8.3 to 68.6mm-chain end over the cation range 2–200mm-Na+ at pH4.5. Action on maltose was only moderately activated (1.3-fold, non-competitively) and action on maltotriose was marginally and competitively inhibited. 3. The pH optimum at 2mm-Na+ was 4.5 (maltose) and 5.1 (glycogen). Cation activation of enzyme action on glycogen was markedly pH-dependent. At 200mm-Na+, the pH optimum was 4.8 and activity was maximally stimulated in the range pH4.5–3.3. 4. Glucosidase action on maltosaccharides was associated with pronounced substrate inhibition at concentrations exceeding 5mm. Of the maltosaccharides tested, the enzyme showed a preference for p-nitrophenyl α-maltoside (Km 1.2mm) and maltotriose (Km 1.8mm). The extrapolated Km for enzyme action on maltose was 3.7mm. 5. The macromolecular polysaccharide substrate glycogen differed from linear maltosaccharide substrates in the kinetics of its interaction with the enzyme. Activity was markedly dependent on pH, cation concentration and polysaccharide structure. There was no substrate inhibition. 6. The enzyme exhibited constitutive α-1,6-glucanohydrolase activity. The Km for panose was 20mm. 7. The enzyme catalysed the total conversion of glycogen into glucose. The hydrolysis of α-1,6-linkages was apparently rate-limiting during the hydrolysis of glycogen. 8. Enzyme action on glycogen and maltose released the α-anomer of d-glucose. 9. The results are discussed in terms of the physiological role of acid α-glucosidase in lysosomal glycogen catabolism.

The direct synthesis of phospho enol pyruvate from pyruvate by Escherichia coli

1967 ◽  
Vol 168 (1012) ◽  
pp. 263-280 ◽  
Keyword(s):  
Escherichia Coli ◽  
Inorganic Phosphate ◽  
Direct Synthesis ◽  
Physiological Role ◽  
Wild Type ◽  
Pyruvate Kinase Activity ◽  
Ph Values ◽  
Direct Formation ◽  
Pyruvate Synthase

Extracts of Escherichia coli are shown to contain an enzyme system which in the presence of Mg 2+ catalyses the direct formation of phospho enol pyruvate from pyruvate and ATP with concomitant formation of AMP and inorganic phosphate. This enzyme, which has been designated 'phospho enol pyruvate synthase' ( PEP -synthase) has been purified 80-fold and is free of pyruvate kinase activity; PEP synthesis proceeded most rapidly at pH 8 to 8.5. At pH values between 6.2 and 7.5 the enzyme can catalyse the formation of ATP and pyruvate from PEP , AMP and inorganic phosphate; if arsenate is used instead of phosphate, pyruvate and ADP are produced instead. Studies of the enzymic formation of PEP with ATP specifically labelled with 32 P, and of the reverse reaction with [U -14 C] AMP , suggest that the PEP -synthase reaction involves the transfer of a pyrophosphoryl-group. The physiological role of PEP -synthase has been demonstrated with mutants of E. coli devoid of the enzyme: in contrast to wild-type organisms, such mutants neither grow on pyruvate, lactate or alanine, nor form glycogen from lactate. It is thus concluded that PEP -synthase plays an important role in the anaplerotic and the biosynthetic reactions which enable the organisms to grow on pyruvate as sole carbon source.

scholarly journals A STUDY OF THE NUCLEOSIDE TRI- AND DIPHOSPHATE ACTIVITIES OF RAT LIVER MICROSOMES

1962 ◽  
Vol 15 (3) ◽  
pp. 563-578 ◽  
Author(s):  
Lars Ernster ◽  
Lois C. Jones
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Physiological Role ◽  
Sodium Deoxycholate ◽  
Inorganic Pyrophosphatase ◽  
Rat Liver Microsomes ◽  
High Concentrations ◽  
Hydrolysis Of ◽  
No Activation

Rat liver microsomes catalyze the hydrolysis of the triphosphates of adenosine, guanosine, uridine, cytidine, and inosine into the corresponding diphosphates and inorganic orthophosphate. The activities are stimulated by Na2S2O4, and inhibited by atebrin, chlorpromazine, sodium azide, and deaminothyroxine. Sodium deoxycholate inhibits the ATPase activity in a progressive manner; the release of orthophosphate from GTP and UTP is stimulated by low, and inhibited by high, concentrations of deoxycholate, and that from CTP and ITP is unaffected by low, and inhibited by high, concentrations of deoxycholate. Subfractionation of microsomes with deoxycholate into ribosomal, membrane, and soluble fractions reveals a concentration of the triphosphatase activity in the membrane fraction. Rat liver microsomes also catalyze the hydrolysis of the diphosphates of the above nucleosides into the corresponding monophosphates and inorganic orthophosphate. Deoxycholate strongly enhances the GDPase, UDPase, and IDPase activities while causing no activation or even inhibition of the ADPase and CDPase activities. The diphosphatase is unaffected by Na2S2O4 and is inhibited by azide and deaminothyroxine but not by atebrin or chlorpromazine. Upon fractionation of the microsomes with deoxycholate, a large part of the GDPase, UDPase, and IDPase activities is recovered in the soluble fraction. Mechanical disruption of the microsomes with an Ultra Turrax Blender both activates and releases the GDPase, UDPase, and IDPase activities, and the former effect occurs more readily than the latter. The GDPase, UDPase, and IDPase activities of the rat liver cell reside almost exclusively in the microsomal fraction, as revealed by comparative assays of the mitochondrial, microsomal, and final supernatant fractions of the homogenate. The microsomes exhibit relatively low nucleoside monophosphatase and inorganic pyrophosphatase activities, and these are unaffected by deoxycholate or mechanical treatment. Different approaches toward the function of the liver microsomal nucleoside tri- and diphosphatases are reported, and the possible physiological role of the two enzymes is discussed.

The Penetration of Acetylcholine into the Central Nervous Tissues of an Insect (Periplaneta Americana L.)

1965 ◽  
Vol 43 (1) ◽  
pp. 13-21
Author(s):  
J. E. TREHERNE ◽  
D. S. SMITH
Keyword(s):  
Synaptic Transmission ◽  
Nerve Cord ◽  
Periplaneta Americana ◽  
Extracellular Fluid ◽  
Physiological Role ◽  
Intracellular Uptake ◽  
Rapid Accumulation ◽  
Stage Process ◽  
Hydrolysis Of

1. 14C-labelled acetylcholine was found to penetrate rapidly into the tissues of the intact abdominal nerve cord. Uptake in the presence of 10-4 M eserine occurred as a two-stage process, the initial rapid influx being identified as the penetration into the extracellular system of the nerve cord. 2. There was a more rapid accumulation of radioactivity in normal preparations as compared with those treated with 10-4 M eserine, presumably as a result of intracellular uptake of the products of hydrolysis of the acetylcholine. 3. The level of radioactivity in the rapidly exchanging fraction was consistent with the hypothesis that the acetylcholine ions were distributed in the extracellular fluid according to a Donnan equilibrium with the haemolymph in eserinized preparations. 4. These results are discussed in relation to the possible physiological role of acetylcholine in synaptic transmission in this insect.

scholarly journals The oxygen isotope composition of phosphate released from phytic acid by the activity of wheat and <i>Aspergillus niger</i> phytase

2015 ◽  
Vol 12 (6) ◽  
pp. 5055-5077
Author(s):  
C. v. Sperber ◽  
F. Tamburini ◽  
B. Brunner ◽  
S. M. Bernasconi ◽  
E. Frossard
Keyword(s):  
Aspergillus Niger ◽  
Oxygen Isotope ◽  
Inorganic Phosphate ◽  
Wheat Germ ◽  
Isotope Composition ◽  
Isotopic Fractionation ◽  
Oxygen Isotope Composition ◽  
Acid Phosphatases ◽  
Enzymatic Assays ◽  
Hydrolysis Of

Abstract. Phosphorus (P) is an essential nutrient for living organisms. Under P-limiting conditions plants and microorganisms can exude extracellular phosphatases that release inorganic phosphate (Pi) from organic phosphorus compounds (Porg). Phytic acid (IP6) is an important form of Porg in many soils. The enzymatic hydrolysis of IP6 by phytase yields plant available inorganic phosphate (Pi) and less phosphorylated inositol derivates as products. The hydrolysis of organic P-compounds by phosphatases leaves an isotopic imprint on the oxygen isotope composition (δ18O) of released Pi, which might be used to trace P in the environment. This study aims at determining the effect of phytase on the oxygen isotope composition of released Pi. For this purpose, enzymatic assays with histidine acid phytases from wheat and Aspergillus niger were prepared using IP6, adenosine 5'monophosphate (AMP) and glycerophosphate (GPO4) as substrates. For a comparison to the δ18O of Pi released by other extracellular enzymes, enzymatic assays with acid phosphatases from potato and wheat germ with IP6 as substrate were prepared. During the hydrolysis of IP6 by phytase, four Pi are released, and one oxygen atom from water is incorporated into each Pi. This incorporation of oxygen from water into Pi is subject to an apparent inverse isotopic fractionation (&amp;varepsilon; ∼ 6 to 10‰), which is similar to that imparted by acid phosphatase from potato during the hydrolysis of IP6 (&amp;varepsilon; ∼ 7‰) where less than three Pi are released. The incorporation of oxygen from water into Pi during the hydrolysis of AMP and GPO4 by phytase yielded a normal isotopic fractionation (&amp;varepsilon; ∼ −12‰), again similar to values reported for acid phosphatases from potato and wheat germ. We attribute this similarity in ε to the same amino acid sequence motif (RHGXRXP) at the active site of these enzymes, which leads to similar reaction mechanisms. We suggest that the striking substrate-dependency of the isotopic fractionation could be attributed to a difference in the δ18O-values of the C-O-P bridging and non-bridging oxygen atoms in organic phosphate compounds.

scholarly journals Molecular and Physiological Role of the Trehalose-Hydrolyzing α-Glucosidase from Thermus thermophilus HB27

2008 ◽  
Vol 190 (7) ◽  
pp. 2298-2305 ◽  
Author(s):  
Susana Alarico ◽  
Milton S. da Costa ◽  
Nuno Empadinhas
Keyword(s):  
Amino Acids ◽  
Minimal Medium ◽  
Thermus Thermophilus ◽  
Physiological Role ◽  
Hydrolytic Activity ◽  
Recombinant Enzyme ◽  
New Feature ◽  
Hydrolysis Of ◽  
Reciprocal Replacement

ABSTRACT Trehalose supports the growth of Thermus thermophilus strain HB27, but the absence of obvious genes for the hydrolysis of this disaccharide in the genome led us to search for enzymes for such a purpose. We expressed a putative α-glucosidase gene (TTC0107), characterized the recombinant enzyme, and found that the preferred substrate was α,α-1,1-trehalose, a new feature among α-glucosidases. The enzyme could also hydrolyze the disaccharides kojibiose and sucrose (α-1,2 linkage), nigerose and turanose (α-1,3), leucrose (α-1,5), isomaltose and palatinose (α-1,6), and maltose (α-1,4) to a lesser extent. Trehalose was not, however, a substrate for the highly homologous α-glucosidase from T. thermophilus strain GK24. The reciprocal replacement of a peptide containing eight amino acids in the α-glucosidases from strains HB27 (LGEHNLPP) and GK24 (EPTAYHTL) reduced the ability of the former to hydrolyze trehalose and provided trehalose-hydrolytic activity to the latter, showing that LGEHNLPP is necessary for trehalose recognition. Furthermore, disruption of the α-glucosidase gene significantly affected the growth of T. thermophilus HB27 in minimal medium supplemented with trehalose, isomaltose, sucrose, or palatinose, to a lesser extent with maltose, but not with cellobiose (not a substrate for the α-glucosidase), indicating that the α-glucosidase is important for the assimilation of those four disaccharides but that it is also implicated in maltose catabolism.

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