Combined pressure and cosolvent effects on enzyme activity – a high-pressure stopped-flow kinetic study on α-chymotrypsin

2015 ◽  
Vol 17 (35) ◽  
pp. 23273-23278 ◽  
Author(s):  
Trung Quan Luong ◽  
Roland Winter
Keyword(s):  
High Pressure ◽  
Enzyme Activity ◽  
Kinetic Study ◽  
Stopped Flow ◽  
Hydrolysis Of ◽  
Cosolvent Effects

Pressure enhances the hydrolysis of peptides catalysed by α-CT, which is efficiently and differently modulated by chaotropic and kosmotropic cosolvents.

scholarly journals KINETIC STUDY ON ANIONIC σ-COMPLEX FORMATION BETWEEN 2,4,6-TRINITROANISOLE AND METHOXIDE ION BY HIGH PRESSURE STOPPED-FLOW METHOD

1979 ◽  
Vol 8 (6) ◽  
pp. 671-674 ◽  
Author(s):  
Noboru Takisawa ◽  
Muneo Sasaki ◽  
Fujitsugu Amita ◽  
Jiro Osugi
Keyword(s):  
High Pressure ◽  
Complex Formation ◽  
Kinetic Study ◽  
Stopped Flow ◽  
Flow Method ◽  
Methoxide Ion

scholarly journals Stopped-Flow Kinetic Study of Reduction of Ferric Maltol Complex by Ascorbate

2016 ◽  
Vol 12 (4) ◽  
pp. 4338-4341
Author(s):  
Shabana Amin ◽  
Shazia Nisar ◽  
S Arif Kazmi
Keyword(s):  
Kinetic Study ◽  
Acid Hydrolysis ◽  
Rate Constant ◽  
Free Ligand ◽  
Low Ph ◽  
Reducing Agent ◽  
The Other ◽  
Stopped Flow ◽  
Kinetic Investigation ◽  
Hydrolysis Of

Stopped-flow kinetic investigation of reduction of Fe(III)-maltol complex is reported. The rates are dependent on pH in a complex way. On one hand at low pH there is a predominance of Fe(III)(maltol)2 which is easier to reduce compared to Fe(III) (maltol)3 which is more resistant to reduction. On the other hand ascorbate is a stronger reducing agent at higher pH. The rates are also found to be inversely dependent on the concentration of free ligand. These observations are explained by the following rate law:Rate = ((k0 +k1[H+])k2 [Asc-]/ (k-1[HMal] + k2[Asc-])) + k3 [Asc-] ) [FeIII(Mal)3] Here k1 is the rate constant for acid hydrolysis of the Fe(maltol)3 complex to Fe(maltol)2 complex and is directly controlled by H+, k0 is the rate constant for hydrolysis of the Fe(maltol)3 complex to Fe(maltol)2 complex and is an intrinsic process, k-1 is the rate constant of reformation of the tris complex by reaction of the bis complex and the free ligand, k2 is the rate constant for reduction of the bis complex by ascorbate and k3 is the rate constant for the reduction of the tris complex by ascorbate.

scholarly journals The hydrolysis of nicotinamide adenine nucleotide by brush border membranes of rat intestine

1982 ◽  
Vol 204 (1) ◽  
pp. 203-207 ◽  
Author(s):  
C L Baum ◽  
J Selhub ◽  
I H Rosenberg
Keyword(s):  
High Pressure ◽  
Enzyme Activity ◽  
Brush Border ◽  
Membrane Fraction ◽  
Brush Border Membrane ◽  
Adenine Nucleotide ◽  
Rat Intestine ◽  
Nicotinamide Riboside ◽  
Nicotinamide Mononucleotide ◽  
Hydrolysis Of

The hydrolysis of NAD by rat intestine was studied to determine the subcellular site of this hydrolysis and to identify the niacin-containing products that are formed. Using [nicotinamide-14C]NAD as substrate, and high pressure liquid chromatography for identification and quantification of products, the present study demonstrates two independent reactions for the hydrolysis of NAD; one that forms nicotinamide through hydrolysis of the ribosyl-pyridinium bond and one that forms nicotinamide mononucleotide through the hydrolysis of the pyrophosphate bond. The nicotinamide mononucleotide is subsequently dephosphorylated to nicotinamide riboside. Enzymes which release nicotinamide mononucleotide and nicotinamide riboside are associated with the brush border membrane as determined by analysis of fractionated intestinal homogenates. The enzyme activity which releases nicotinamide from NAD is associated with the brush border membrane fraction and also with a second cellular particulate fraction. Between pH5 and pH6 NAD is hydrolysed principally to nicotinamide. At pH 7.0 rates of nicotinamide and nicotinamide mononucleotide formation are the same. Above pH 7.0 the formation of nicotinamide mononucleotide is preferred.

Benzyl ethers of methyl α-D-glucopyranoside

1980 ◽  
Vol 45 (7) ◽  
pp. 1959-1963 ◽  
Author(s):  
Dušan Joniak ◽  
Božena Košíková ◽  
Ludmila Kosáková
Keyword(s):  
Kinetic Study ◽  
Spectrophotometric Determination ◽  
Reductive Cleavage ◽  
Ether Bond ◽  
Benzyl Ethers ◽  
Acid Catalyzed ◽  
Model Substances ◽  
Hydrolysis Of

Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.

Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1557-1570 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Ilmar A. Koppel
Keyword(s):  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Solvent Parameters ◽  
Substituent Constants ◽  
Hydrolysis Of ◽  
Main Factor

The second-order rate constants k2 (dm3 mol-1 s-1) for the alkaline hydrolysis of substituted alkyl benzoates C6H5CO2R have been measured spectrophotometrically in aqueous 0.5 M Bu4NBr at 50 and 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH, CH2C6H5, CH2CH2Cl, CH2CH2OCH3, CH2CH3) and in aqueous 5.3 M NaClO4 at 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH). The dependence of the alkyl substituent effects on different solvent parameters was studied using the following equations:      ∆ log k = c0 + c1σI + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆EσI + c7∆YσI + c8∆PσI     ∆ log k = c0 + c1σ* + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆Eσ* + c7∆Yσ* + c8∆Pσ* .  ∆ log k = log kR - log kCH3. σI and σ* are the Taft inductive and polar substituent constants. E, Y and P are the solvent electrophilicity, polarity and polarizability parameters, respectively. In the data treatment ∆E = ES - EH2O , ∆Y = YS - YH2O , ∆P = PS - PH2O were used. The solvent electrophilicity, E, was found to be the main factor responsible for changes in alkyl substituent effects with medium. When σI constants were used, variation of the polar term of alkyl substituents with the solvent electrophilicity E was found to be similar to that observed earlier for meta and para substituents, but twice less when σ* constants were used. The steric term for alkyl substituents was approximately independent of the solvent parameters.

A Kinetic Study of the Copper(II) Chelate Catalyzed Hydrolysis of Diisopropyl Phosphorofluoridate

1963 ◽  
Vol 85 (5) ◽  
pp. 598-601 ◽  
Author(s):  
Richard L. Gustafson ◽  
Stanley. Chaberek ◽  
Arthur E. Martell
Keyword(s):  
Kinetic Study ◽  
Diisopropyl Phosphorofluoridate ◽  
Hydrolysis Of
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