Spectral and kinetic properties of a cationic peroxidase secreted by cultured peanut cells

1985 ◽  
Vol 63 (10) ◽  
pp. 1086-1092 ◽  
Author(s):  
Anne-Marie Lambeir ◽  
H. Brian Dunford ◽  
Robert B. van Huystee ◽  
Jerzy Lobarzewski
Keyword(s):  
Dissociation Constant ◽  
Native Enzyme ◽  
Kinetic Properties ◽  
Compound I ◽  
Prosthetic Group ◽  
Equilibrium Studies ◽  
Alkaline Transition ◽  
Cyanide Binding ◽  
Ph Range ◽  
Compound Ii

It is demonstrated that the cationic peroxidase isolated from the growth medium of cultured peanut cells reacts via the same mechanism as other peroxidases, namely conversion of the native enzyme into compound I by reaction with hydrogen peroxide, followed by two reductions by one-electron donors to compound II and then back to the native enzyme. From the pyridine hemochromogen spectrum it is concluded that the prosthetic group of the native enzyme is ferriprotoporphyrin IX. Optical spectra are recorded for (i) the native (ferric) enzyme and its cyanide, azide, fluoride and alkaline forms, (ii) ferrous peroxidase and its cyanide and carbon monoxide complexes, and (iii) compounds I, II, and III. Equilibrium studies show that the ferric cyanide complex has a dissociation constant of 3.0 ± 0.5 μM over the pH range 3–8. The fluoride complex has a dissociation constant which varies from 1.6 μM at pH 4.0 to 28 μM at pH 4.8. Azide has a much lower affinity than fluoride. The alkaline transition occurs with an apparent pKa value of 9.2. Rate constants were recorded for cyanide binding, the alkaline transition, compound I formation, and for the reactions of compound II with a series of substrates. Similarities and differences to horseradish peroxidase are discussed.

Redox properties of the couples compound I/compound II and compound II/native enzyme of human myeloperoxidase

2003 ◽  
Vol 301 (2) ◽  
pp. 551-557 ◽  
Author(s):  
Paul Georg Furtmüller ◽  
Jürgen Arnhold ◽  
Walter Jantschko ◽  
Hans Pichler ◽  
Christian Obinger
Keyword(s):  
Redox Properties ◽  
Native Enzyme ◽  
Compound I ◽  
Compound Ii

Studies on Horseradish Peroxidase. XII. A Kinetic Study of the Oxidation of Sulfite and Nitrite by Compounds I and II

1973 ◽  
Vol 51 (4) ◽  
pp. 588-596 ◽  
Author(s):  
R. Roman ◽  
H. B. Dunford
Keyword(s):  
Horseradish Peroxidase ◽  
Ground State ◽  
Ph Dependence ◽  
Intermediate Formation ◽  
Ion Concentration ◽  
Compound I ◽  
Hydrogen Ion Concentration ◽  
Ph Range ◽  
Compound Ii ◽  
Kinetics Of

The kinetics of the oxidation of sulfite and nitrite by horseradish peroxidase compounds I and II have been studied as a function of pH at 25° and ionic strength 0.11. The pH dependence of the rate of the reaction between compound I and sulfite over the pH range 2–7 is interpreted in terms of two ground state enzyme dissociations with pka values of 5.1 and 3.3, and that for the compound II reaction with sulfite in terms of a single ground state enzyme dissociation with a pKa value of 3.9. Whereas the reaction between compound I and sulfite produces the native enzyme without the intermediate formation of compound II, the reaction of compound I with nitrite yields compound II. The second-order rate constants for the reactions of compounds I and II with nitrite increase linearly with increasing hydrogen ion concentration over the pH range 6–8.

Kinetics of formation of the primary compound (compound I) from hydrogen peroxide and turnip peroxidases

1978 ◽  
Vol 56 (7) ◽  
pp. 702-707 ◽  
Author(s):  
Dominique Job ◽  
Jacques Ricard ◽  
H. Brian Dunford
Keyword(s):  
Hydrogen Peroxide ◽  
Compound I ◽  
Ph Profile ◽  
Glycerol Water ◽  
Binding Reaction ◽  
Cyanide Binding ◽  
Kinetics Of Formation ◽  
Ph Range ◽  
Kinetics Of ◽  
Ionizable Groups

A kinetic study of the reaction of two turnip peroxidases (P1 and P7) with hydrogen peroxide to form the primary oxidized compound (compound I) has been carried out over the pH range from 2,4 to 10.8. In the neutral and acidic pH regions, the rates depend linearly on hydrogen peroxide concentration whereas at alkaline pH values the rates display saturation kinetics. A comparison is made with the cyanide binding reaction to peroxidases since the two reactions are influenced in the same manner by ionization of groups on the native enzymes. Two different ionization processes of peroxidase P1 with pKa values of 3.9 and 10 are required to explain the rate pH profile for the reaction with H2O2. Protonation of the former group and ionization of the latter causes a decrease in the rate of reaction of the enzyme with H2O2. In the case of peroxidase P7 a minimum model involves three ionizable groups with pKa values of 2.5, 4, and 9. Protonation of the former two groups and ionization of the latter lowers the reaction rate. In the pH-independent region, the rate of formation of compound I was measured as a function of temperature. From the Arrhenius plots the activation energy for the reaction was calculated to be 2.9 ± 0.1 kcal/mol for P1 and 5.4 ± 0.3 kcal/mol for P7. However, the rates are independent of viscosity in glycerol–water mixtures up to 30% glycerol.

scholarly journals Horseradish peroxidase. XXIX. Reactions in water and deuterium oxide: cyanide binding, compound I formation, and reactions of compounds I and II with ferrocyanide

1978 ◽  
Vol 56 (22) ◽  
pp. 2844-2852 ◽  
Author(s):  
H. Brian Dunford ◽  
W. Donald Hewson ◽  
Håkan Steiner
Keyword(s):  
Hydrogen Peroxide ◽  
Horseradish Peroxidase ◽  
Kinetic Isotope Effect ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Compound I ◽  
Kinetic Isotope ◽  
Cyanide Binding ◽  
Compound Ii

The kinetics of the reactions of hydrogen peroxide and cyanide with native horseradish peroxidase, as well as reactions of compounds I and II with ferrocyanide have been studied in ordinary water and in deuterium oxide at 25 °C and ionic strength 0.11 using a stopped-flow apparatus. Rate constants for all reactions were measured over a wide range of acidity in both solvents from which equilibrium and kinetic isotope effects were evaluated. Protonation of an ionizable group on the enzyme with a pKa value of 4.15 ± 0.05 in water inhibits the reactions with both hydrogen peroxide and cyanide. A significant kinetic isotope effect, kH/kD = 1.6 ± 0.1, was measured for compound I formation whereas no significant kinetic isotope effect was found for cyanide binding. On the basis of these findings, a partial mechanism for compound I formation is proposed in which the group of pKa 4.15 plays a crucial role. The pH dependencies of the ferrocyanide reaction in the pH interval 4.5–10.8 confirmed the role of an acid group with a pKa of 5.2 for compound I and for compound II a pKa of 8.6 and another with a value lower than that encompassed by the pH range of the study. Equilibrium isotope effects were found but no kinetic isotope effects for either the reaction of compound I or of compound II This suggests that there are no rate-limiting proton transfers in the reactions between ferrocyanide and compounds I and II of horseradish peroxidase. The only reducing substrates which exhibit positive kH/kD values possess a labile proton.

Horseradish peroxidase. XLII. Oxidations of L-tyrosine and 3,5-diiodo-L-tyrosine by compound II

1980 ◽  
Vol 58 (11) ◽  
pp. 1270-1276 ◽  
Author(s):  
Isobel M. Ralston ◽  
H. Brian Dunford
Keyword(s):  
Horseradish Peroxidase ◽  
Reaction Rate ◽  
Acid Group ◽  
Amino Groups ◽  
Compound I ◽  
Ph Profile ◽  
Rate Versus ◽  
Phenolic Group ◽  
Ph Range ◽  
Compound Ii

The oxidations of both L-tyrosine and 3,5-diiodo-L-tyrosine by compound II of horseradish peroxidase were studied over the pH range of approximately 3 to 10 at 25 °C and at a constant ionic strength of 0.11. The rate versus pH profile for the tyrosine – compound II reaction illustrates the influences of at least two acid group ionizations. An enzyme dissociation (pKa ~ 6.2) has a small effect on the reaction rate; whereas, a second pKa of 9.2, which may be attributed to either the enzyme or substrate, has a greater influence on the rate. The oxidation of tyrosine by compound II is fastest at pH 7.6. In the case of the diiodotyrosine – compound II reaction, three acid dissociations are necessary to describe the plot of log (kapp) versus pH. These include two enzyme pKa values of 3.6 and 8.6, and one substrate pKa of 6.6. The rate optimum for the reaction occurs at pH 5.2 and deprotonation of the phenolic group of diiodotyrosine results in a dramatic decrease in kapp. Diiodotyrosine is required in only a 0.5 M equivalent for the conversion of horseradish peroxidase compound I to compound II. The diiodotyrosine pKa values were estimated as 6.4 and 9.4 for the phenolic and amino groups, respectively.

Kinetics of oxidation of serotonin by myeloperoxidase compounds I and II

1999 ◽  
Vol 77 (5) ◽  
pp. 449-457 ◽  
Author(s):  
H Brian Dunford ◽  
Yuchiong Hsuanyu
Keyword(s):  
Rate Constant ◽  
Blood Platelets ◽  
Transient State ◽  
Order Rate Constant ◽  
Compound I ◽  
Kinetic Measurements ◽  
Order Of Magnitude ◽  
Electron Reduction ◽  
Ph Range ◽  
Compound Ii

The oxidation of serotonin (5-hydroxytryptamine) by the myeloperoxidase intermediates compounds I and II was investigated by using transient-state spectral and kinetic measurements at 25.0 ± 0.1°C. Rapid scan spectra demonstrated that both compound I and compound II oxidize serotonin via one-electron processes. Rate constants for these reactions were determined using both sequential-mixing and single-mixing stopped-flow techniques. The second order rate constant obtained for the one-electron reduction of compound I to compound II by serotonin is (1.7 ± 0.1) × 107 M-1·s-1, and that for compound II reduction to native enzyme is (1.4 ± 0.1) × 106 M-1·s-1 at pH 7.0. The maximum pH of the compound I reaction with serotonin occurs in the pH range 7.0-7.5. At neutral pH, the rate constant for myeloperoxidase compound I reacting with serotonin is an order of magnitude larger than for its reaction with chloride, (2.2 ± 0.2) × 106 M-1·s-1. A direct competition of serotonin with chloride for myeloperoxidase compound I oxidation was observed. Our results suggest that serotonin may have a role to protect lipoproteins from oxidation and to prevent enzymes from inactivation caused by the potent oxidants HOCl and active oxygen species.Key words: serotonin oxidation, myeloperoxidase, chloride, competition of serotonin, blood platelets, neutrophils.

scholarly journals Replacement of enzyme-bound calcium with strontium alters the kinetic properties of methanol dehydrogenase

1994 ◽  
Vol 300 (1) ◽  
pp. 175-182 ◽  
Author(s):  
T K Harris ◽  
V L Davidson
Keyword(s):  
Paracoccus Denitrificans ◽  
Competitive Inhibitor ◽  
Methanol Dehydrogenase ◽  
Native Enzyme ◽  
Kinetic Properties ◽  
Host Bacterium ◽  
Prosthetic Group ◽  
Dependent Activity ◽  
Cyanide Inhibition ◽  
Endogenous Activity

Methanol dehydrogenase (MEDH) possesses tightly bound Ca2+ in addition to its pyrroloquinoline quinone (PQQ) prosthetic group. Ca2+ was replaced with Sr2+ by growing the host bacterium, Paracoccus denitrificans, in media in which Ca2+ was replaced with Sr2+. MEDH, which was purified from these cells (Sr-MEDH), exhibited an increased absorption coefficient for the PQQ chromophore, and displayed certain kinetic properties which were different from those of native MEDH. Native MEDH exhibits an endogenous activity which is not stimulated by substrate and which is inhibited by cyanide. Sr-MEDH exhibited lower endogenous activity which was stimulated by substrate, and was much less sensitive to inhibition by cyanide. The Vmax. for the methanol-dependent activity of Sr-MEDH was 3-fold greater than that of the native enzyme, and the Ks for methanol was altered. Cyanide also acts as an obligatory activator and competitive inhibitor of methanol-dependent activity in native MEDH from P. denitrificans [Harris and Davidson (1993) Biochemistry 32, 4362-4368]. Sr-MEDH exhibited a similar K1 for cyanide inhibition of methanol-dependent activity, but the KA for cyanide activation of this activity was 17-fold greater than that for the native enzyme. The activation energy of Sr-MEDH was 13.4 kJ (3.2 kcal)/mol lower than that of the native enzyme. These data confirm and significantly extend the conclusions from genetic [Richardson and Anthony (1992) Biochem. J. 287, 709-715] and crystallographic [White, Boyd, Mathews, Xia, Dai, Zhang and Davidson (1993) Biochemistry 32, 12955-12958] studies that suggest an apparently unique role for Ca2+ in MEDH compared with other Ca(2+)-dependent proteins and enzymes.

scholarly journals Interplay between Oxo and Fluoro in Vanadium Oxyfluorides for Centrosymmetric and Non-Centrosymmetric Structure Formation

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 603
Author(s):  
Prashanth Sandineni ◽  
Hooman Yaghoobnejad Asl ◽  
Weiguo Zhang ◽  
P. Shiv Halasyamani ◽  
Kartik Ghosh ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Metastable Phase ◽  
Compound I ◽  
Hydrothermal Route ◽  
Prolonged Heating ◽  
Space Group ◽  
Lithium Vanadium Oxide ◽  
Compound Ii ◽  
Unambiguous Assignment ◽  
Centrosymmetric Structure

Herein, we report the syntheses of two lithium-vanadium oxide-fluoride compounds crystallized from the same reaction mixture through a time variation experiment. A low temperature hydrothermal route employing a viscous paste of V2O5, oxalic acid, LiF, and HF allowed the crystallization of one metastable phase initially, Li2VO0.55(H2O)0.45F5⋅2H2O (I), which on prolonged heating transforms to a chemically similar yet structurally different phase, Li3VOF5 (II). Compound I crystallizes in centrosymmetric space group, I2/a with a = 6.052(3), b = 7.928(4), c = 12.461(6) Å, and β = 103.99(2)°, while compound II crystallizes in a non-centrosymmetric (NCS) space group, Pna21 with a = 5.1173(2), b = 8.612(3), c = 9.346(3) Å. Synthesis of NCS crystals are highly sought after in solid-state chemistry for their second-harmonic-generation (SHG) response and compound II exhibits SHG activity albeit non-phase-matchable. In this article, we also describe their magnetic properties which helped in unambiguous assignment of mixed valency of V (+4/+5) for Li2VO0.55(H2O)0.45F5⋅2H2O (I) and +4 valency of V for Li3VOF5 (II).

scholarly journals Crystal structures of {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O}nand {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O}n[where Lpn = (R)-propane-1,2-diamine]: two heterometallic chiral cyanide-bridged coordination polymers

2015 ◽  
Vol 71 (4) ◽  
pp. 392-397
Author(s):  
Olha Sereda ◽  
Helen Stoeckli-Evans
Keyword(s):  
Hydrogen Bonds ◽  
Coordination Polymers ◽  
Three Dimensional ◽  
Water Molecules ◽  
Two Dimensional ◽  
Asymmetric Unit ◽  
Compound I ◽  
Distorted Octahedral ◽  
Coordination Spheres ◽  
Compound Ii

The title compounds,catena-poly[[[bis[(R)-propane-1,2-diamine-κ2N,N′]copper(II)]-μ-cyanido-κ2N:C-[tris(cyanido-κC)(nitroso-κN)iron(III)]-μ-cyanido-κ2C:N] monohydrate], {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O}n, (I), and poly[[hexa-μ-cyanido-κ12C:N-hexacyanido-κ6C-hexakis[(R)-propane-1,2-diamine-κ2N,N′]dichromium(III)tricopper(II)] pentahydrate], {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O}n, (II) [where Lpn = (R)-propane-1,2-diamine, C3H10N2], are new chiral cyanide-bridged bimetallic coordination polymers. The asymmetric unit of compound (I) is composed of two independent cation–anion units of {[Cu(Lpn)2][Fe(CN)5)(NO)]} and two water molecules. The FeIIIatoms have distorted octahedral geometries, while the CuIIatoms can be considered to be pentacoordinate. In the crystal, however, the units align to form zigzag cyanide-bridged chains propagating along [101]. Hence, the CuIIatoms have distorted octahedral coordination spheres with extremely long semicoordination Cu—N(cyanido) bridging bonds. The chains are linked by O—H...N and N—H...N hydrogen bonds, forming two-dimensional networks parallel to (010), and the networks are linkedviaN—H...O and N—H...N hydrogen bonds, forming a three-dimensional framework. Compound (II) is a two-dimensional cyanide-bridged coordination polymer. The asymmetric unit is composed of two chiral {[Cu(Lpn)2][Cr(CN)6]}−anions bridged by a chiral [Cu(Lpn)2]2+cation and five water molecules of crystallization. Both the CrIIIatoms and the central CuIIatom have distorted octahedral geometries. The coordination spheres of the outer CuIIatoms of the asymmetric unit can be considered to be pentacoordinate. In the crystal, these units are bridged by long semicoordination Cu—N(cyanide) bridging bonds forming a two-dimensional network, hence these CuIIatoms now have distorted octahedral geometries. The networks, which lie parallel to (10-1), are linkedviaO—H...O, O—H...N, N—H...O and N—H...N hydrogen bonds involving all five non-coordinating water molecules, the cyanide N atoms and the NH2groups of the Lpn ligands, forming a three-dimensional framework.

Zolmitriptan oxalate and zolmitriptan camphorsulfonate: the first structural study of salt complexes of the antimigraine drug zolmitriptan

2013 ◽  
Vol 69 (10) ◽  
pp. 1186-1191
Author(s):  
Balasubramanian Sridhar ◽  
Krishnan Ravikumar ◽  
Venkatasubramanian Hariharakrishnan
Keyword(s):  
Structural Study ◽  
Three Dimensional ◽  
Helical Chain ◽  
Side Chain ◽  
Indole Ring ◽  
Asymmetric Unit ◽  
Compound I ◽  
Space Group ◽  
Compound Ii ◽  
Ring Motif

Zolmitriptan hydrogen oxalate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium hydrogen oxalate], C16H22N3O2+·C2HO4−, (I), and zolmitriptan camphorsulfonate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium (S,R)-{2-hydroxy-7,7-dimethylbicyclo[2.2.1]heptan-1-yl}methanesulfonate], C16H22N3O2+·C10H15O4S−, (II), are the first reported salt complexes of the antimigraine drug zolmitriptan. Compound (I) crystallizes in the space groupP21with two molecules of protonated zolmitriptan and two oxalate monoanions in the asymmetric unit, while compound (II) crystallizes in the space groupP212121with one protonated zolmitriptan molecule and one camphorsulfonate anion in the asymmetric unit. The orientations of the ethylamine side chain and the oxazolidinone ring with respect to the indole ring of the zolmitriptan cation are different for (I) and (II). In (I), they are oriented in opposite directions and the molecule adopts a step-like appearance, while in (II) the corresponding side chains are folded in the same direction, giving the molecule a cup-like appearance. The zolmitriptan molecules of (I) form anR22(8) dimer, while in (II) they form a helical chain with aC(11) motif. The oxalate monoanions of (I) interact with the zolmitriptan cations and extend the dimer into a three-dimensional hydrogen-bonded network. In (II), the camphorsulfonate anion forms anR22(15) ring motif with the zolmitriptan cation.

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