Iodoacetate inactivation of rape alcohol dehydrogenase

1980 ◽  
Vol 45 (5) ◽  
pp. 1601-1607 ◽  
Author(s):  
Marie Stiborová ◽  
Sylva Leblová
Keyword(s):  
Alcohol Dehydrogenase ◽  
Protein Molecule ◽  
Sulfhydryl Groups ◽  
Inactivation Rate ◽  
First Order ◽  
Ph Dependent ◽  
Kinetics Of

Iodoacetate inactivates rape alcohol dehydrogenase (ADH, EC 1.1.1.1). The inactivation rate follows the kinetics of the first order, is pH-dependent, and decreases below pH 7.5. Besides irreversible alkylation of the sulfhydryl groups of the enzyme iodoacetate also forms a reversible complex with rape ADH. The coenzyme (NAD) and its analogs (ATP, ADP, AMP) competitively protect the enzyme against alkylation; o-phenanthroline also protects the enzyme against alkylation yet noncompetitively with respect to iodoacetate. Imidazole and o-phenanthroline compete with one another for binding to the protein molecule of rape ADH. Whereas o-phenanthroline decreases the inactivation rate imidazole increases the rate of iodoacetate inactivation.

scholarly journals Mechanistic studies of carboxypeptidase Y from Saccharomyces cerevisiae. pH and pD profiles and inactivation at low pH (pD) values

1980 ◽  
Vol 187 (3) ◽  
pp. 843-849 ◽  
Author(s):  
W T Chang ◽  
K T Douglas
Keyword(s):  
Tertiary Structure ◽  
Low Ph ◽  
Carboxypeptidase Y ◽  
Mechanistic Studies ◽  
Ph Profile ◽  
First Order ◽  
Steady State Kinetics ◽  
Ph Dependent ◽  
Kinetics Of ◽  
Hydrolysis Of

Steady-state kinetics of carboxypeptidase Y, a proteinase from yeast, were studied by using the reaction of 4-nitrophenyl trimethylacetate as a probe. The pH profile of kcat. is sigmoidal in H2O-based buffers for the carboxypeptidase Y-catalysed hydrolysis of this ester (kcat. referring to the rate of deacylation of trimethylacetyl-carboxypeptidase Y). The corresponding pD profile in 2H2O is doubly sigmoidal, with inflexions at pD approximately 3.8 and approximately 6.8. The ionization of pKDapp. approximately 3.8 is caused by a rapid inactivation in 2H2O media by a process that is only slowly reversed on transfer to pH 7.00 phosphate buffer in H2O. The corresponding inactivation in H2O-based buffers of low pH is considerably slower (approximately 30-fold), follows a first-order rate-dependence and is very strongly pH-dependent, indicating some form of co-operative change in enzyme tertiary structure.

scholarly journals Mechanism of initiation of aggregation of p53 revealed by Φ-value analysis

2015 ◽  
Vol 112 (8) ◽  
pp. 2437-2442 ◽  
Author(s):  
GuoZhen Wang ◽  
Alan R. Fersht
Keyword(s):  
Protein Molecule ◽  
Bimolecular Reaction ◽  
Tumor Suppressor P53 ◽  
Reaction Conditions ◽  
Value Analysis ◽  
Mutant Proteins ◽  
First Order ◽  
First Order Kinetics ◽  
Oncogenic Mutations ◽  
Kinetics Of

Many oncogenic mutations inactivate the tumor suppressor p53 by destabilizing it, leading to its rapid aggregation. Small molecule drugs are being developed to stabilize such mutants. The kinetics of aggregation of p53 is deceptively simple. The initial steps in the micromolar concentration range follow apparent sigmoidal sequential first-order kinetics, with rate constants k1 and k2. However, the aggregation kinetics of a panel of mutants prepared for Φ-value analysis has now revealed a bimolecular reaction hidden beneath the observed first-order kinetics. Φu measures the degree of local unfolding on a scale of 0–1. A number of sequential Φu-values of ∼1 for k1 and k2 over the molecule implied more than one protein molecule must be reacting, which was confirmed by finding a clear concentration dependence at submicromolar protein. Numerical simulations showed that the kinetics of the more complex mechanism is difficult, if not impossible, to distinguish experimentally from simple first order under many reaction conditions. Stabilization of mutants by small molecules will be enhanced because they decrease both k1 and k2. The regions with high Φu-values point to the areas where stabilization of mutant proteins would have the greatest effect.

Urokinase Activation of Plasminogen and Spontaneous Inactivation of the Plasmin Formed

1968 ◽  
Vol 19 (01/02) ◽  
pp. 145-160 ◽  
Author(s):  
W Berg
Keyword(s):  
Order Reaction ◽  
Zero Order ◽  
Inactivation Rate ◽  
First Order Reaction ◽  
Activity Levels ◽  
First Order ◽  
Activation Rate ◽  
Zero Order Reaction ◽  
High Concentrations ◽  
Kinetics Of

SummaryThe kinetics of the activation of plasminogen into plasmin with urokinase and the inactivation rate of the plasmin formed are studied.As a first order reaction is obtained with low plasminogen concentrations and a zero-order reaction is obtained with high concentrations, the activation seems to follow the Michaelis-Menten’s law. The reaction does not go to completion, however. Different activity levels, which are dependent on the urokinase concentration, can be observed.The activation rate increases with temperature. A maximum can be seen at about 42° C.Between 4° C and 15° C, the inactivation of the plasmin formed is minimal, but it increases rapidly at higher temperatures. The inactivation follows approximately a first order reaction with respect to time. If the plasminogen concentration is low, the over-all reaction will be that of two consecutive first order reactions.

scholarly journals STUDIES ON THE CONFORMATIONAL CHANGES OF MITOCHONDRIAL MALATE DEHYDROGENASE IN UREA–PHOSPHATE SOLUTIONS

1967 ◽  
Vol 45 (5) ◽  
pp. 659-669 ◽  
Author(s):  
R. J. Seguin ◽  
G. W. Kosicki
Keyword(s):  
Malate Dehydrogenase ◽  
Conformational Changes ◽  
Inorganic Phosphate ◽  
Protein Molecule ◽  
Order Rate Constant ◽  
Sulfhydryl Groups ◽  
First Order ◽  
Phosphate Ions ◽  
Mitochondrial Malate Dehydrogenase ◽  
Phosphate Solutions

Pig-heart mitochondrial malate dehydrogenase is gradually inactivated in 4 M urea. During the inactivation, sulfhydryl groups on the protein are exposed in a first-order reaction. The reaction is followed spectrophotometricaily using the sulfhydryl reagent, 5,5′-dithiobis(2-nitrobenzoate) (DTNB). Titration with DTNB in the presence of urea exposes 10 to 12 sulfhydryl groups per molecule of mitochondrial malate dehydrogenase. The enzyme is also inactivated when diluted in water but no sulfhydryl groups are unmasked. The loss of activity and the appearance of sulfhydryl groups in urea solutions do not take place at the same rate.The conformational changes of malate dehydrogenase that occur in urea solutions are partially prevented by inorganic phosphate ions, and less so by the substrates NADH, NAD+, oxalacetate (OAA), and L-malate. The protection against loss of enzyme activity by inorganic phosphate ions is pH-dependent. Both inorganic phosphate and NADH considerably reduce the first-order rate constant for sulfhydryl appearance in 4 M urea. Protection of the enzyme against sulfhydryl appearance in urea solutions by pre-incubation with the substrates indicates that about two sulfhydryl groups per molecule of mitochondrial malate dehydrogenase are involved in substrate binding. Thus, the substrates must keep the active site of the enzyme intact. They either bind to the sulfhydryl groups or prevent the protein molecule from completely unfolding.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH < 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

The Kinetics of Glucose Decomposition with Sulfate Reduction in the Anaerobic Fluidized Bed Reactor

1993 ◽  
Vol 28 (2) ◽  
pp. 135-144 ◽  
Author(s):  
S. Matsui ◽  
R. Ikemoto Yamamoto ◽  
Y. Tsuchiya ◽  
B. Inanc
Keyword(s):  
Sulfate Reduction ◽  
Fluidized Bed ◽  
Kinetic Equations ◽  
Fluidized Bed Reactor ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Glucose Decomposition ◽  
Reaction Equations ◽  
Kinetics Of

Using a fluidized bed reactor, experiments on glucose decomposition with and without sulfate reduction were conducted. Glucose in the reactor was mainly decomposed into lactate and ethanol. Lactate was mainly decomposed into propionate and acetate, while ethanol was decomposed into propionate, acetate, and hydrogen. Sulfate reduction was not involved in the decomposition of glucose, lactate, and ethanol, but was related to propionate and acetate decomposition. The stepwise reactions were modeled using either a Monod expression or first order reaction kinetics in respect to the reactions. The coefficients of the kinetic equations were determined experimentally. The modified Monod and first order reaction equations were effective at predicting concentrations of glucose, lactate, ethanol, propionate, acetate, and sulfate along the beight of the reactor. With sulfate reduction, propionate was decomposed into acetate, while without sulfate reduction, accumulation of propionate was observed in the reactor. Sulfate reduction accelerated propionate conversion into acetate by decreasing the hydrogen concentration.

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

Kinetics of catalytic reduction of nitrogen oxide by carbon monoxide on CuO/Al2O3 catalyst

1983 ◽  
Vol 48 (11) ◽  
pp. 3202-3208 ◽  
Author(s):  
Zdeněk Musil ◽  
Vladimír Pour
Keyword(s):  
Carbon Monoxide ◽  
Nitrogen Oxide ◽  
Rate Equation ◽  
Catalytic Reduction ◽  
Zero Order ◽  
Spectroscopic Measurements ◽  
First Order ◽  
Ir Spectroscopic ◽  
Kinetics Of ◽  
Al2o3 Catalyst

The kinetics of the reduction of nitrogen oxide by carbon monoxide on CuO/Al2O3 catalyst (8.36 mass % CuO) were determined at temperatures between 413 and 473 K. The reaction was found to be first order in NO and zero order in CO. The observed kinetics are consistent with a rate equation derived from a mechanism proposed on the basis of IR spectroscopic measurements.

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