scholarly journals ENZYME KINETICS IN A HISTOCHEMICAL SYSTEM

1958 ◽  
Vol 6 (6) ◽  
pp. 431-434 ◽  
Author(s):  
EARL P. BENDITT ◽  
MARGARET ARASE
Keyword(s):  
Chemical Kinetics ◽  
Enzyme System ◽  
The Other ◽  
End Point ◽  
Straight Line ◽  
Spontaneous Hydrolysis ◽  
Fixed Quantity ◽  
Set Up ◽  
Kinetics Of ◽  
Hydrolysis Of

Modification of the Lineweaver and Burk method of handling the chemical kinetics of an enzyme system has been made to suit the histochemical conditions. Thus if the reaction is allowed to run to some fixed quantity of end point 1/v becomes proportion to the time necessary to reach this end point. In practice serial dilutions of substrate and serial increments in time of incubation are set up. Slides are then separated under the microscope into groups of equal intensity. A plot of 1/[S] v.s. t fits a straight line as expected. Competition between two substrates, one chromogenic the other non-chromogenic, can be demonstrated. One source of deviation from the theoretical due to spontaneous hydrolysis of substrate has been recognized and can be accounted for.

Inhibition of the elastase of Pseudomonas aeruginosa by N.alpha.-phosphoryl dipeptides and kinetics of spontaneous hydrolysis of the inhibitors

Biochemistry ◽  
1984 ◽  
Vol 23 (12) ◽  
pp. 2766-2772 ◽  
Author(s):  
Louis Poncz ◽  
Thomas A. Gerken ◽  
Dorr G. Dearborn ◽  
Damian Grobelny ◽  
Richard E. Galardy
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Spontaneous Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the acid and alkaline hydrolysis of methyl fluoride in water

1952 ◽  
Vol 211 (1105) ◽  
pp. 254-265 ◽  
Keyword(s):  
Alkaline Hydrolysis ◽  
The Other ◽  
Methyl Halides ◽  
Methyl Fluoride ◽  
Rate Determining Step ◽  
Hydroxyl Ion ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Kinetic Features

The kinetics of the reaction of methyl fluoride with water and the hydroxyl ion have been determined experimentally at various concentrations and temperatures. The results are compared with the data available on the other methyl halides. The mechanism of the anionic reaction is discussed in terms of a hypothesis according to which the rate-determining step is the partial desolvation of the ion. This mechanism is extended to account also for the kinetic features of the hydrolysis.

scholarly journals The Contractile and Control Sites of Natural Actomyosin

1967 ◽  
Vol 50 (10) ◽  
pp. 2421-2435 ◽  
Author(s):  
Harvey M. Levy ◽  
Elizabeth M. Ryan
Keyword(s):  
Control System ◽  
Driving Force ◽  
Inhibitory Action ◽  
Atp Hydrolysis ◽  
The Other ◽  
Contractile System ◽  
Contraction And Relaxation ◽  
And Control ◽  
Kinetics Of ◽  
Hydrolysis Of

The various contractile and control sites of natural actomyosin gel were studied by comparing the kinetics of ATP hydrolysis with those of gel contraction, measured as an increase in turbidity. Contraction of actomyosin gel seems to require the cooperative reaction of ATP (with Mg) at two different sites. One of these sites catalyzes the hydrolysis of ATP and most probably contributes the driving force for contraction; the binding of ATP to the other site appears to break certain links that retard movement of the gel components. At limiting concentrations of ATP, the rate of contraction seems to depend on the rate of breaking these links as well as on the rate of ATP hydrolysis. But when both sites are saturated, the rate of contraction appears to be limited only by the rate of ATP hydrolysis. In addition to these two contractile sites, there are also two different control sites. At one, the relaxing site, the binding of ATP with Mg inhibits ATP hydrolysis and gel contraction. At the other, the binding of calcium activates contraction by overcoming the inhibitory action of Mg and ATP at the relaxing site. This control system—inhibition by substrate and disinhibition by calcium—can be selectively inactivated by heat and reactivated by dithiothreitol, a disulfide-reducing agent. These observations on the isolated contractile system are discussed in relation to the contraction and relaxation of muscle.

Kinetics of α-chymotrypsin action. I. pH, solvent, and temperature effects

1967 ◽  
Vol 45 (5) ◽  
pp. 547-557 ◽  
Author(s):  
Harvey Kaplan ◽  
K. J. Laidler
Keyword(s):  
Dielectric Constant ◽  
Low Temperature ◽  
Temperature Effects ◽  
Methyl Esters ◽  
The Other ◽  
Kcal Mole ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Ph Variations

An investigation has been made of the influence of pH on the kinetics of the α-chymotrypsin-catalyzed hydrolysis of N-acetyl-l-tyrosine ethyl ester, p-nitrophenyl acetate, and N-benzoyl-d- and -l-alanine methyl esters. From the pH variations of [Formula: see text], and [Formula: see text], it is deduced that in the free enzyme there are ionizing groups of pK 6.9 and 9.2. From the variation of these pK values with dielectric constant, it is concluded that, when protonated, one group is cationic and the other neutral. A temperature-dependence study was carried out on N–benzoyl-d- and -l-alanine methyl esters. The sharp break in the plot of log [Formula: see text] against 1/T is attributed to a rapid reversible denaturation of the enzyme at the higher temperatures. In the low-temperature region, the activation energies are ΔEL = 16.2 ± 0.3 kcal/mole and ΔED = 16.5 ± 0.6 kcal/mole.

THE WHEAT LEAF PHOSPHATASES: VI. SOME PROPERTIES OF THE ENZYME SYSTEM HYDROLYZING ADENOSINE-5′-PHOSPHATE AND PHENOLPHTHALEIN DIPHOSPHATE IN CRUDE JUICE PREPARATIONS

1963 ◽  
Vol 41 (5) ◽  
pp. 1275-1281 ◽  
Author(s):  
D. W. A. Roberts
Keyword(s):  
Enzyme System ◽  
The Other ◽  
Enzymic Hydrolysis ◽  
Ph Optimum ◽  
Wheat Leaf ◽  
Hydrolysis Of ◽  
Leaf Juice

At least two enzymes are probably involved in the hydrolysis of mixtures of β-glycerophosphate, phenolphthalein diphosphate, and adenosine-5′-phosphate. One enzyme is primarily responsible for the hydrolysis of β-glycerophosphate whereas the other enzyme hydrolyzes adenosine-5′-phosphate and phenolphthalein diphosphate but has little activity on β-glycerophosphate.The liberation of orthophosphate from adenosine-5′-phosphate and phenolphthalein diphosphate by the enzyme in wheat leaf juice is inhibited by 0.005 M adenosine but not by 0.02 M phosphate. The inhibition of this enzyme by fluoride is markedly smaller than the inhibition of β-glycerophosphatase. The enzyme that hydrolyzes phenolphthalein diphosphate transfers phosphate from phenolphthalein diphosphate to adenosine to form adenosine-5′-phosphate.Experiments on the pH optimum for the enzymic hydrolysis of both adenosine-5′-phosphate and phenolphthalein diphosphate by undialyzed and dialyzed juice preparations with or without added Mg++ suggest that there may be more than one enzyme with different pH optima acting on both adenosine-5′-phosphate and phenolphthalein diphosphate.

scholarly journals The heterogeneous chemical kinetics of N<sub>2</sub>O<sub>5</sub> on CaCO<sub>3</sub> and other atmospheric mineral dust surrogates

2005 ◽  
Vol 5 (5) ◽  
pp. 10369-10408
Author(s):  
F. Karagulian ◽  
C. Santschi ◽  
M. J. Rossi
Keyword(s):  
Gas Phase ◽  
Chemical Kinetics ◽  
Mineral Dust ◽  
Saharan Dust ◽  
Molecular Flow ◽  
Flow Conditions ◽  
Heterogeneous Chemical ◽  
Powder Samples ◽  
Kinetics Of ◽  
Hydrolysis Of

Abstract. Uptake experiments of N2O5 on several mineral dust powder samples were carried out under continuous molecular flow conditions at 298±2 K. At [N2O5]0=(4.0±1.0)×1011 cm−3 we have found γss values ranging from (3.5±1.1)×10−2 for CaCO3 to (0.20±0.05) for Saharan Dust with γss decreasing as [N2O5]0 increased. We have observed delayed production of HNO3 upon uptake of N2O5 for every investigated sample owing to hydrolysis of N2O5 with surface-adsorbed H2O. At high and low [N2O5] Arizona Test Dust and Kaolinite turned out to be the samples to produce the largest amount of gas phase HNO3 with respect to N2O5 taken up. In contrast, the yield of HNO3 for Saharan Dust and CaCO3 are lower. On CaCO3 the disappearance of N2O5 was also accompanied by the formation of CO2. For CaCO3 sample masses ranging from 0.33 to 2.0 g, the yield of CO2 was approximately 42–50% with respect to the total number of N2O5 molecules taken up. The reaction of N2O5 with mineral dust and the subsequent production of gas phase HNO3 leads to a decrease in [NOx] which may have a significant effect on global ozone.

THE WHEAT LEAF PHOSPHATASES: VI. SOME PROPERTIES OF THE ENZYME SYSTEM HYDROLYZING ADENOSINE-5′-PHOSPHATE AND PHENOLPHTHALEIN DIPHOSPHATE IN CRUDE JUICE PREPARATIONS

1963 ◽  
Vol 41 (1) ◽  
pp. 1275-1281 ◽  
Author(s):  
D. W. A. Roberts
Keyword(s):  
Enzyme System ◽  
The Other ◽  
Enzymic Hydrolysis ◽  
Ph Optimum ◽  
Wheat Leaf ◽  
Hydrolysis Of ◽  
Leaf Juice

At least two enzymes are probably involved in the hydrolysis of mixtures of β-glycerophosphate, phenolphthalein diphosphate, and adenosine-5′-phosphate. One enzyme is primarily responsible for the hydrolysis of β-glycerophosphate whereas the other enzyme hydrolyzes adenosine-5′-phosphate and phenolphthalein diphosphate but has little activity on β-glycerophosphate.The liberation of orthophosphate from adenosine-5′-phosphate and phenolphthalein diphosphate by the enzyme in wheat leaf juice is inhibited by 0.005 M adenosine but not by 0.02 M phosphate. The inhibition of this enzyme by fluoride is markedly smaller than the inhibition of β-glycerophosphatase. The enzyme that hydrolyzes phenolphthalein diphosphate transfers phosphate from phenolphthalein diphosphate to adenosine to form adenosine-5′-phosphate.Experiments on the pH optimum for the enzymic hydrolysis of both adenosine-5′-phosphate and phenolphthalein diphosphate by undialyzed and dialyzed juice preparations with or without added Mg++ suggest that there may be more than one enzyme with different pH optima acting on both adenosine-5′-phosphate and phenolphthalein diphosphate.

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