The influence of pH on the rates of enzyme reactions. Part 4.—The hydrolysis of methyl hydrocinnamate catalyzed by α-chymotrypsin

SummaryThe specificity of chymosin on αs1-casein was shown to be dependent on the reaction pH and on the state of aggregation of the substrate. In aqueous solution αs1-casein was optimally hydrolysed to αs1-I at pH 5·8; if the casein was solubilized in the isoelectric region by the use of 5 M-urea, optimum proteolysis occurred at pH 2·8. Hydrolysis of αs1-I to yield αs1-II, αs1-III and αs1-IV occurred at pH values > 5·8 in the presence or absence of urea. In the isoelectric region αs1-II, αs1-III and αs1-IV were not formed in the absence of urea where the substrate was aggregated: instead a peptide αs1-V was produced; at the same pH and using urea as a solubilizing agent αs1-II, αs1-III and αs1-IV were formed together with a further peptide αs1-VI.

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The influence of pH and inhibitors on the kinetics of enzyme reactions involving two intermediates

Canadian Journal of Chemistry ◽

10.1139/v67-090 ◽

1967 ◽

Vol 45 (5) ◽

pp. 539-546 ◽

Cited By ~ 12

Author(s):

Harvey Kaplan ◽

Keith J. Laidler

Keyword(s):

Steady State ◽

Ph Dependence ◽

Free Enzyme ◽

State Equations ◽

Enzyme Reactions ◽

Substrate Complex ◽

Rate Determining Step ◽

Enzyme Substrate ◽

Special Cases ◽

Influence Of Ph

General steady-state equations are worked out for enzyme reactions which occur according to the scheme [Formula: see text]Equations showing the pH dependence of the kinetic parameters are developed in a form which distinguishes between essential and nonessential ionizing groups. The pK dependence of [Formula: see text], the second-order constant extrapolated to zero substrate constant, gives pK values for groups which ionize on the free enzyme, but reveals such a pK only if the corresponding group is also involved in the breakdown of the Michaelis complex. General steady-state equations are also developed for the case in which an inhibitor can combine with the free enzyme, the enzyme–substrate complex, and also a second intermediate (e.g. an acyl enzyme). The equations are given in a form that is convenient for analyzing the experimental results, and a number of special cases are considered. It is shown how the type of inhibition depends not only on the nature of the inhibitor but also on that of the substrate, an important factor being the rate-determining step of the reaction. Examples of the various kinds of behavior are given.

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The influence of pH on the rates of enzyme reactions. Part 1.—General theory

Transactions of the Faraday Society ◽

10.1039/tf9555100528 ◽

1955 ◽

Vol 51 (0) ◽

pp. 528-539 ◽

Cited By ~ 39

Author(s):

Keith J. Laidler

Keyword(s):

General Theory ◽

Enzyme Reactions ◽

Influence Of Ph

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ELECTROFLOTATION TREATMENT OF DAIRY WASTEWATER: CHEMICAL-TECHNOLOGICAL ASPECTS

Municipal economy of cities ◽

10.33042/2522-1809-2021-1-161-141-147 ◽

2021 ◽

Vol 1 (161) ◽

pp. 141-147

Author(s):

Ye. Makarov

Keyword(s):

Aqueous Solution ◽

Ferric Chloride ◽

Iron Hydroxide ◽

Electricity Consumption ◽

Dairy Wastewater ◽

Pre Treatment ◽

Experimental Researches ◽

Influence Of Ph ◽

High Processing ◽

Hydrolysis Of

Experimental researches are carried out and chemical-technological laws of reagent-electroflotation treatment of sewage of dairies are established. The wastewater of the milk processing enterprise of Sumy region was selected for the study. For reagent wastewater treatment, ferric chloride FeCl3 in the form of a 5% aqueous solution is selected. To accelerate the hydrolysis of the reagent as an alkaline additive was used calcium oxide (lime) CaO in dry form and sodium hydroxide NaOH in the form of 5% aqueous solution. To accelerate the formation of sediment (sludge) used flocculant nonionic polyacrylamide (PAA) in the form of 0.05% aqueous solution. The efficiency of treatment was studied by the following indicators of wastewater: hydrogen pH, transparency and amount of ether-soluble substances. It is established that the process of extraction of ether-soluble substances largely depends on the pH of the medium and increases with increasing alkalinity of wastewater. The greatest influence of pH of the environment is observed at concentration of FeCl3 of 100-150mg / dm3. When FeCl3 is added at a concentration of 200mg / dm3, the purification effect does not depend on the pH of the medium. The most effective is the addition of ferric chloride and then lime. Initially, the addition of FeCl3 coagulates proteins and partially demulsifies the fat emulsion. After the introduction of lime into the water, hydrolysis and formation of iron hydroxide Fe(OH)3 occurs, on the surface of which contaminants are adsorbed. The greatest degree of purification from ether-soluble substances 87-88% is provided by addition of ferric chloride FeCl3 in concentration of 150-200mg / dm3 at pH of 9,5-10. It was found that when using lime to increase the pH of wastewater at a concentration of 500mg / dm3, there is a more efficient removal of ether-soluble substances and suspended solids (increased transparency), and less sediment is formed. Summarizing the obtained data, the optimal concentrations of reagents for pre-treatment of wastewater were selected – FeCl3 - 100mg / dm3, CaO - 500mg / dm3 and wastewater pH - 7.2. It is shown that the reduction of the content of ether-soluble substances to 40mg / dm3 (at the maximum permissible concentration for dairy wastewater 50mg / dm3) is possible only at high processing time (20-30 minutes) and density (0.05A / cm2) and voltage (26 V) electric current, which leads to high electricity consumption.

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