scholarly journals The effect of temperature on the individual stages of the hydrolysis of non-specific-p-nitrophenol esters by α-chymotrypsin

1977 ◽  
Vol 161 (1) ◽  
pp. 83-92 ◽  
Author(s):  
P A Adams ◽  
E R Swart
Keyword(s):  
Kinetic Studies ◽  
Detailed Comparison ◽  
Effect Of Temperature ◽  
Thermal Transitions ◽  
Arrhenius Plots ◽  
Ph Values ◽  
The Individual ◽  
Hydrolysis Of

Precise studies were performed on the effect of temperature on the rate and equilibrium parameters characterizing the individual stages of the alpha-chymotrypsin-catalysed hydrolysis of non-specific p-nitrophenol esters at pH 7.40 and 8.50. At both pH values the results indicate that a sharp kinetic anomaly is observed in Arrhenius plots of these parameters for the binding and acylation stages of the process, but not for the deacylation stage. Detailed comparison with other kinetic studies was made, and a comparison with thermal transitions observed in alpha-chymotrypsin by using physical techniques was attempted. A detailed discussion of possible causes of the anomalies is given.

scholarly journals SIMULTANEOUS HYDROLYSES OF ESTERS AND PROTEINS AT SATURATION LEVELS

1958 ◽  
Vol 41 (3) ◽  
pp. 485-500 ◽  
Author(s):  
M. Castañeda-Agulló ◽  
Luz M. Del Castillo
Keyword(s):  
Enzyme System ◽  
Kinetic Studies ◽  
Direct Titration ◽  
Enzyme Substrate ◽  
Constant Ph ◽  
Potentiometric Measurement ◽  
The Individual ◽  
Hydrolysis Of ◽  
Protein Enzyme

A direct titration method for the determination of proteolytic activity is discussed. This involves the potentiometric measurement of the volume of 0.08 N NaOH required to maintain a constant pH (8.0) during the time of the hydrolysis. It is a sensitive method which presents several advantages; viz., it measures simultaneously protease and esterase activity, it follows the hydrolysis very closely and from the first stages; the titration is continuous and on the same sample. This method determines a constant fraction of the groups titratable by formol titration. The ratio formol: direct titration is represented by a factor "f" which is presumed to be distinct for each protein-enzyme system. Kinetic studies, using this method, revealed that the rates of hydrolysis of mixtures casein-gelatin on one hand, casein-BAEE or gelatin-BAEE on the other, are always larger than those of the corresponding isolated substrates. In many cases the resulting rates are equal or nearly equal to the sum of the individual rates, even though the mentioned rates have been determined within the saturation zones for every substrate. The former observations are inconsistent with the theory of the formation of an intermediary enzyme-substrate compound, unless it is assumed that the enzyme has a specific active group for each substrate.

scholarly journals Cryoenzymology of trypsin. A detailed kinetic study of the trypsin-catalysed hydrolysis of N-α-benzyloxycarbonyl-l-lysine p-nitrophenyl ester at low temperatures

1983 ◽  
Vol 215 (3) ◽  
pp. 555-563 ◽  
Author(s):  
J P G Malthouse ◽  
A I Scott
Keyword(s):  
Aqueous Media ◽  
Side Chain ◽  
Ambient Temperatures ◽  
Ph Values ◽  
Mechanism Of Catalysis ◽  
The Individual ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Nitrophenyl Ester ◽  
Positively Charged

A detailed study of the kinetics of the trypsin (EC 3.4.21.4)-catalysed hydrolysis of N-alpha-benzyloxycarbonyl-L-lysine p-nitrophenyl ester in cryosolvents at 0 degrees C and below was undertaken. The pH-dependences of kcat, Km, k+2, k+3 and Ks were determined under cryoenzymological conditions and are compared with previous results [Antonini & Ascenzi (1981) J. Biol. Chem. 256, 12449-12455] obtained in fully aqueous media at ambient temperatures. Below pH 5.0 the kinetics, and presumably the mechanism of catalysis, are not significantly perturbed under cryoenzymological conditions. However, it is shown that below pH 5.0 both Km and Ks are decreased under these conditions but that both are increased at pH 6.7 relative to the results obtained in fully aqueous media at ambient temperatures. The effects of the cryoenzymological conditions on the individual catalytic parameters are discussed. The acylation rate constant, k+2, is essentially constant at pH 4.2 and 5.0 but decreases at lower pH values with an apparent pKa of approx. 4.0. In view of the low enthalpy of ionization associated with this pKa it is suggested that this group is the carboxy group of aspartic acid-189, which binds the positively charged lysine side chain of the substrate. The mechanistic implications of the results for the acylation step are discussed. It is also shown that only at low pH values can significant amounts of acylated trypsin be accumulated.

scholarly journals β-Glucosidase Activity of Lactiplantibacillus plantarum UNQLp 11 in Different Malolactic Fermentations Conditions: Effect of pH and Ethanol Content

Fermentation ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 22
Author(s):  
Natalia S. Brizuela ◽  
Marina Arnez-Arancibia ◽  
Liliana Semorile ◽  
María Ángeles Pozo-Bayón ◽  
Bárbara M. Bravo-Ferrada ◽  
...  
Keyword(s):  
Pinot Noir ◽  
Gas Chromatography Mass Spectrometry ◽  
Red Wines ◽  
Ph Values ◽  
Glucosidase Activity ◽  
Sorptive Extraction ◽  
Ethanol Content ◽  
Volatile Precursors ◽  
Hydrolysis Of ◽  
High Ethanol

Lactiplantibacillus plantarum strain UNQLp 11 is a lactic acid bacterium with the potential to carry out malolactic fermentation (MLF) in red wines. Recently, the complete genome of UNQLp 11 was sequenced and this strain possesses four loci of the enzyme β-glucosidase. In order to demonstrate that these glucosidase enzymes could be functional under harsh wine conditions, we evaluated the hydrolysis of p-nitrophenyl-β-D-glucopyranoside (p-NPG) in synthetic wine with different ethanol contents (0%, 12%, and 14% v/v) and at different pH values (3.2, 3.5, and 3.8). Then, the hydrolysis of precursor n-octyl β-D-glucopyranoside was analyzed in sterile Pinot Noir wine (containing 14.5% v/v of ethanol, at different pH values) by headspace sorptive extraction gas chromatography-mass spectrometry (HSSE-GC/MS). The hydrolysis of p-NPG showed that β-glucosidase activity is very susceptible to low pH but induced in the presence of high ethanol content. Furthermore, UNQLp 11 was able to release the glycosilated precursor n-octyl, during MLF to a greater extent than a commercial enzyme. In conclusion, UNQLp 11 could improve the aromatic profile of the wine by the release of volatile precursors during MLF.

Preparation and structural analysis of (±)-threo-ritalinic acid

2013 ◽  
Vol 69 (11) ◽  
pp. 1225-1228 ◽  
Author(s):  
Sara Wyss ◽  
Irmgard A. Werner ◽  
W. Bernd Schweizer ◽  
Simon M. Ametamey ◽  
Selena Milicevic Sephton
Keyword(s):  
Methyl Ester ◽  
Free Acid ◽  
Nmr Analysis ◽  
Intermolecular Hydrogen Bonds ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ph Values ◽  
Ritalinic Acid ◽  
Methyl Phenidate ◽  
Hydrolysis Of

Hydrolysis of the methyl ester (±)-threo-methyl phenidate afforded the free acid in 40% yield,viz.(±)-threo-ritalinic acid, C13H17NO2. Hydrolysis and subsequent crystallization were accomplished at pH values between 5 and 7 to yield colourless prisms which were analysed by X-ray crystallography. Crystals of (±)-threo-ritalinic acid belong to theP21/nspace group and form intermolecular hydrogen bonds. An antiperiplanar disposition of the H atoms of the (HOOC—)CH—CHpygroup (py is pyridine) was found in both the solid (diffraction analysis) and solution state (NMR analysis). It was also determined that (±)-threo-ritalinic acid conforms to the minimization of negativegauche+–gauche−interactions.

Modelling the individual cell lag phase: effect of temperature and pH on the individual cell lag distribution of

2005 ◽  
Vol 100 (1-3) ◽  
pp. 41-53 ◽  
Author(s):  
K FRANCOIS ◽  
F DEVLIEGHERE ◽  
K SMET ◽  
A STANDAERT ◽  
A GEERAERD ◽  
...  
Keyword(s):  
Individual Cell ◽  
Effect Of Temperature ◽  
Lag Phase ◽  
Phase Effect ◽  
The Individual

Micellar catalysis of organic reactions. VIII. Kinetic studies of the hydrolysis of 2-acetyloxybenzoic acid (aspirin) in the presence of micelles

1982 ◽  
Vol 35 (7) ◽  
pp. 1357 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Aqueous Solution ◽  
Cetyltrimethylammonium Bromide ◽  
Cetylpyridinium Chloride ◽  
Kinetic Studies ◽  
Base Catalysis ◽  
Plateau Region ◽  
General Base ◽  
Mechanism Of Hydrolysis ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of 2-acetyloxybenzoic acid in the pH range 6-12 has been studied in the presence of micelles of cetyltrimethylammonium bromide (ctab) and cetylpyridinium chloride (cpc). In the plateau region (pH 6-8) the hydrolysis is inhibited by the presence of micelles, while in the region where the normal BAC2 hydrolysis (pH > 9) occurs the reaction is catalysed by micelles of ctab and cpc. The mechanism of hydrolysis in the plateau region is shown to involve general base catalysis by the adjacent ionized carboxy group both in the presence and absence of micelles. This reaction is inhibited in the presence of micelles because the substrate molecules are solubilized into the micelle and water is less available in this environment than in normal aqueous solution.

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