Cytochemical studies on leukemic cells. I. Stable Nadi oxidase, peroxidase, DOPA oxidase and Sudan black B reaction.
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A commercial glucose oxidase (GOX) from Aspergillus niger was partially characterized. The enzyme exhibited a two-step transfer mechanism, and the kinetic constants toward glucose and oxygen were determined. Under conditions similar to dough making (glucose concentration and pH), GOX does not exhibit maximum activity. A hexose oxidase (HOX) from Chondrus crispus was partially characterized as well. The HOX activity is not far from the optimum in the kneading conditions (pH and glucose concentration). A peroxidase (POD) purified from wheat germ was used to oxidize ferulic acid in the presence of GOX or HOX. Hydrogen peroxide produced during the glucose oxidation activates the wheat germ POD. Ferulic acid oxidation in solutions containing different ratios of POD + GOX or HOX + POD was followed by UV spectrophotometry. For the same dosage, the HOX-POD system is the most efficient for peroxidase activation. Using absorbance data and kinetic constants of GOX and POD, a mathematical model describing the release or consumption of the different reactants (hydrogen peroxide, oxygen, and ferulic acid) in the medium was developed, and experimental data correlated well with calculated values. The results obtained will be applied to investigate the effect of GOX and HOX activities on the rheological properties of dough.
The nonlinear behavior of the peroxidase-oxidase reaction was studied using structurally different peroxidases. For the first time sustained oscillations with peroxidases other than horseradish peroxidase in a single-enzyme system were observed. All peroxidases that showed significant oxidase activity were able to generate sustained oscillations. When adjusting the overall reaction rate, either of the two modifiers 2,4-dichlorophenol or Methylene blue could be omitted from the reaction. Due to the observation of different enzyme intermediates when using different peroxidases, we conclude that the mechanisms responsible for oscillatory kinetics may vary from one peroxidase to the other.
Oscillatory kinetics in the peroxidase-oxidase reaction catalyzed by structurally different peroxidases were investigated using NADH as a substrate. For horseradish peroxidase, lactoperoxidase, and soybean peroxidase the oscillatory waveforms of their dominating enzyme intermediates, ferric peroxidase and compound III, are similar. Coprinus peroxidase, on the other hand, has ferrous peroxidase and compound III as the dominating intermediates. The oscillatory waveform of its compound III differs from the waveforms of compound III of the three other peroxidases. Also, the phase plot of the signal for compound III versus the oxygen concentration for Coprinus peroxidase differs from the corresponding phase plots obtained using other peroxidases. A detailed model of the reaction mechanism is proposed, which is able to simulate these different kinds of behaviour. Substituting NADH with dihydroxyfumaric acid as a substrate, oscillations in the oxygen concentration were observed for about 1.5 h when a concentrated solution of this substrate was continuously fed to a solution containing horseradish peroxidase. This is the first demonstration of sustained oscillations with this substrate.
The abilities of various peroxidases to catalyse the peroxidase-oxidase oxidation of seven aminothiols were studied. Cysteamine and cysteine esters were found to be peroxidase-oxidase substrates for eosinophil peroxidase and myeloperoxidase, whereas other thiols tested were inactive or poorly active with these peroxidases. With lactoperoxidase and horseradish peroxidase, all the tested thiols were inactive or poorly active as peroxidase-oxidase substrates. These studies suggest that a main reason for thiols being poor peroxidase-oxidase substrates is because these thiols are poor peroxidatic substrates.
The oscillatory peroxidase-oxidase reaction has been investigated by using NADH deuterated in the nicotinamide 4-A position. A considerable kinetic hydrogen/deuterium isotope effect on the oscillatory behavior was revealed, which may provide an additional valuable tool for mechanistic studies and for discriminating between various mechanistic models of the peroxidase-oxidase reaction. Particularly, this effect manifests in different oscillation frequencies. A sequence of simple and aperiodic oscillations was found between two stable steady states.
Cysteamine and reduced glutathione were shown to act synergistically as peroxidase-oxidase substrates as measured by oxygen consumption and Nitro Blue Tetrazolium reduction. Cysteine methyl ester could be substituted for cysteamine and N-acetylcysteine and penicillamine could be substituted for glutathione. The involvement of reduced oxygen species and the effects of pH and chloride were studied. A possible mechanism of peroxidase-oxidase oxidation of cysteamine and glutathione is proposed. These studies show that peroxidase oxidase reactions can occur with close to physiological concentrations of peroxidase and thiols.
The influence of a series of naturally occurring phenolic compounds on the dynamics of the horseradish peroxidase-catalyzed oxidation of NADH by oxygen (the peroxidase-oxidase reaction) was investigated. Various types of dynamic behaviors are induced in the peroxidase-oxidase reaction upon addition of low concentrations of different phenols. The identity of the particular phenol determines the type of dynamics shown (inhibition of the reaction, monotonic reaction, damped oscillations, sustained oscillations, and complex oscillations). The kind of behavior that a given phenolic compound is able to induce is governed by the reduction potentials for the formation of the phenoxyl radical. The phenolic compounds are shown not to be consumed during the reaction. Mechanistic considerations are made on the basis of the reduction potentials of the different reactants present in the peroxidase-oxidase system. We interpret the role of the phenols as electron mediators of the electron transfer between some enzyme intermediates or O2- and NADH.
Melatonin induces oscillations in the peroxidase-oxidase (PO) reaction catalyzed by horseradish peroxidase. We present here studies of the effect of pH, enzyme concentration, and concentration of melatonin on the oscillation frequency. We also present a mechanistic model to explain the experimentally observed changes in oscillation frequency. Using the data obtained here we are able to predict that oscillations will also occur in the PO reaction catalyzed by myeloperoxidase. Myeloperoxidase is an important protein in activated neutrophils and we provide evidence that the oscillations of NAD(P)H, superoxide and hydrogen peroxide in these cells may involve this enzyme. Thus, our experimental system can be considered a model system for the nonrespiratory oxygen metabolism in activated neutrophils and other similar cells participating in the defence against invading pathogens.
We have studied the peroxidase-oxidase reaction catalyzed by human myeloperoxidase in an open system where both substrates-molecular oxygen and NADH-are supplied continuously to the reaction mixture. The reaction shows oscillatory kinetics at pH values around 5, provided that the reaction medium in addition to the enzyme and the substrates also contains an aromatic electron mediator such as melatonin or 4-hydroxybenzoic acid and chloride ions at concentrations >1mM. The experimental findings can be simulated by a detailed model of the reaction. The results are important for our understanding of oxidant production in neutrophils.
An enzyme system from Datura innoxia roots oxidizing formylphenylacetic acid ethyl ester was purified 38-fold by conventional methods such as (NH4)2SO4 fractionation, negative adsorption on alumina Cy gel and chromatography on DEAE-cellulose. The purified enzyme was shown to catalyse the stoicheiometric oxidation of formylphenylacetic acid ethyl ester to benzoylformic acid ethyl ester and formic acid, utilizing molecular O2. Substrate analogues such as phenylacetaldehyde and phenylpyruvate were oxidized at a very low rate, and formylphenylacetonitrile was an inhilating agents, cyanide, thiol compounds and ascorbic acid. This enzyme was identical with an oxidase-peroxidase isoenzyme. Another oxidase-peroxidase isoenzyme which separated on DEAE-chromatography also showed formylphenylacetic acid ethyl ester oxidase activity, albeit to a lesser extent. The properties of the two isoenzymes of the oxidase were compared and shown to differ in their oxidation and peroxidation properties. The oxidation of formylphenylacetic acid ethyl ester was also catalysed by horseradish peroxidase. The Datura isoenzymes exhibited typical haemoprotein spectra. The oxidation of formylphenylacetic acid ethyl ester was different from other peroxidase-catalysed reactions in not being activated by either Mn2+ or monophenols. The oxidation was inhibited by several mono- and poly-phenols and by catalase. A reaction mechanism for the oxidation is proposed.
Human immunodeficiency virus type 1 (HIV-1) is rapidly inactivated by exposure to a naturally occurring antimicrobial system consisting of peroxidase, H2O2, and a halide. Among the potential sources of H2O2 is the amine oxidase system in which mono-, di-, and polyamines are oxidatively deaminated with the formation of H2O2. The polyamine spermine is present at exceptionally high concentrations in semen. We report here that spermine, spermidine, and, to a lesser degree, the synthetic polyamine 15-deoxyspergualin are viricidal to HIV-1 when combined with amine oxidase and myeloperoxidase. Antiviral activity required each component of the spermine-amine oxidase-peroxidase system and was inhibited by azide (a peroxidase inhibitor) and by catalase but not by superoxide dismutase. Heat treatment of catalase largely abolished its inhibitory effect. These findings implicate H2O2 formed by the amine oxidase system in the antiviral effect and raise the possibility that the polyamine-amine oxidase-peroxidase system influences the survival of HIV-1 in semen and in the vaginal canal.
NADH chemistry ancillary to the oscillatory peroxidase-oxidase (PO) reaction has been reexamined. Previously, (NAD)2 has been thought of as a terminal, inert product of the PO reaction. We now show that (NAD)2 is a central reactant in this system. Although we found traces of the dimer after several hours of the PO reaction, no accumulation of the dimer occurred, regardless of the reaction time or the number of oscillations. (NAD)2 can convert horseradish peroxidase (HRP) compound I (CpI) to compound II (CpII) with apparent rate constant (2.7 +/- 0.2) x 105 M-1.s-1 and CpII to HRP at 1 x 105 M-1.s-1. Moreover, a reduction of HRP compound III (CpIII) to CpI by (NAD)2 occurs with a rate constant faster than 5 x 106 M-1.s-1. The (NAD)2 reduction of CpIII provides an alternative to the reduction by NAD radical suggested by Yokota and Yamazaki. HRP catalyzes oxidation of alpha-NADH, not only the beta anomer as previously assumed. Rate constants of alpha- and beta-NADH reactions with CpI are (7.4 +/- 0.4) x 105 M-1.s-1, and (1.7 +/- 0.2) x 105 M-1.s-1, and with CpII are estimated as 5 x 104 M-1.s-1, and 4 x 104 M-1.s-1. Apparent rate constants of reduction of methylene blue (MB) to leuco-methylene blue (MBH) are 3.8 x 104 M-1.s-1 for NADH and 6.4 x 104 M-1.s-1 for NAD dimer, (NAD)2, while reoxidation of MBH proceeds at (2.1 +/- 0.2) x 103 M-1.s-1 All the rates were measured in 0.1 M acetate buffer, pH 5.1.
Inherent variance due to oscillations in the peroxidase-oxidase (PO) reaction was studied using principal component analysis (PCA). The substrates were oxygen and reduced nicotinamide adenine dinucleotide (NADH). Horseradish peroxidase (HRP) catalyzed the reaction. The concentration of a cofactor, methylene blue (MB), was varied, and 2,4-dichlorophenol was kept constant. Increase in the NADH influx was used to change the reaction dynamics from periodic to chaotic. The reaction space was abstracted to the most significant, mutually independent, pairs of absorption and kinetic basis vectors (principal components). Typically, two significant principal components were extracted from the periodic time series and three from the chaotic data. The PCA models accounted for 70-97% of experimental variance. The greatest fraction of the total variance was accounted for in experiments exhibiting periodic dynamics and less than 25 nM MB. More MB induced an increased contribution of NADH to the PO oscillator variance, as did increased NADH influx. A simulated absorption time series, computed from a mass-action model of the chemistry, was analyzed by PCA as well. The comparison of simulation with experiment indicates that the chemical model renders the time series for HRP oxidation forms with fidelity, but incompletely represents NADH chemistry and other salient processes underlying the observed dynamics.
In experiments on the kinetics of the peroxidase-oxidase oscillatory reaction in pH 5.l acetate buffer, biofilms form in less than 48 h on the quartz reactor surface. The nominally homogeneous peroxidase system shows dynamical changes in response to this biofilm growth, partially explaining subtle differences among dynamics observed over time and between laboratories. Kinetics data and model computations are correlated with micrographs of biofilm formation. It is evident that bare quartz also interacts with reaction species, so that the surface area-to-volume ratio is an important parameter on which observed dynamics depend.
We have studied the peroxidase-oxidase reaction with NADH and O2 as substrates and melatonin as a cofactor in a semibatch reactor. We show for the first time that melatonin is an activator of the reaction catalyzed by enzymes from both plant and animal sources. Furthermore, melatonin promotes oscillatory dynamics in the pH range from 5 to 6. The frequency of the oscillations depends on the pH such that an increase in pH was accompanied by a decrease in frequency. Conversely, an increase in the flow rate of NADH or an increase in the average concentration of NADH resulted in an increase in oscillation frequency. Complex dynamics were not observed with melatonin as a cofactor. These results are discussed in relation to observations of oscillatory dynamics and the function of melatonin and peroxidase in activated neutrophils.
The influence of temperature on the oscillatory kinetics of the peroxidase-oxidase reaction was studied theoretically. Assuming Q(10)=2 for elementary reactions, the effect of multiplying the rate constants of the model by factors between 0.5 and 2 (corresponding to a 10 degrees C decrease and increase, respectively, of temperature) was investigated. First, the individual rate constants were successively multiplied by 0.5 or 2 while all other rate constants were kept unchanged. This resulted in either a longer or a shorter period, depending on the rate constant being changed. Multiplication by 0.5 or by 2 generally resulted in opposite effects on the period length. However, the absolute value of this deviation differed. Also, the dynamics changed when halving the dimerization rate of NAD* as well as when doubling the rate constant for the reduction of ferric peroxidase by NAD*. Next, simulations were performed multiplying all rate constants by one and the same factor, which increased progressively from 0.5 to 2. Intervals were found corresponding to temperature dependency, compensation, and over-compensation, respectively.
A multiple time scale analysis of two four-variable models of the peroxidase-oxidase reaction, the DOP, and the Olsen model, is carried out. It is shown that autonomous limit cycle oscillations are exhibited by the fast subsets of these two models, but only in certain regions of parameter space, confirming the prior suggestion that the slow variable (NADH) is not essential for oscillatory behavior. However, it is found that the slow variable is essential for oscillatory behavior over other ranges of parameter values, and is always essential for complex oscillatory and chaotic behavior. This latter conclusion is based on a study involving driving the fast subset with a sinusoidally varying (NADH). This study suggests the level of coupling between fast and slow variables of an autonomous system necessary to cause the chaos observed in the DOP model. Further study of the driven system allows for the identification of a natural period of the nonoscillatory but bistable fast subsystem and a set of rules for applying a parametric driving in such a way as to generate a more complete Farey sequence from a truncated Farey sequence. These conclusions are used to compare the very similar DOP and Olsen models, which, nevertheless, exhibit quite different Farey sequences and routes to chaos. (c) 1995 American Institute of Physics.