Constant catalytic

The kinetic data for the action of plasmin on different substrates under various conditions have been summarized. The MichaeHs-Menten constant (iC ) varies between 10 and 1000 mAf and the catalytic constant between 1 and 75. ... 

This equation contains a further term, ko, representing the solvent (water) term. In any given system, any of these terms may of course be negligible. The values of the catalytic constants and kon can be determined at the pH extremes. This equation states that the rate will be a minimum at an intermediate pH. It is easy to show that this occurs at a pH independent of ko, as expressed by... 

Catalytic Constants and Activation Parameters for the Enzymic Hydrolysis of /i-D-Glucopyranosides ... 

KDHRF A homologous restriction factor binds to C8 65KDHRF A homologous restriction factor, also known as C8 binding protein interferes with cell membrane pore-formation by C5b-C8 complex Kcat Catalytic constant a measure of the catalytic potential of an enzyme Ka Equilibrium dissociation constant kD Kilodalton Kd Dissociation constant KD Kallidin... 

Catalytic Coal Liquid (CCL) process, 6 848 Catalytic coke yield, 11 705 Catalytic constant, 10 254 Catalytic converter(s), 10 31, 39 40 26 719. See also Three-way catalytic converter... 

It has been shown by H naff (1963) that the rate of reaction of several carbonyl reagents (bisulphite, hydrazine, phenylhydrazine, semi-carbazide and hydroxylamine) with aqueous formaldehyde solutions is independent of the nature and concentration of the reagent, and is therefore determined by the rate of dehydration of methylene glycol. He obtained catalytic constants for hydrogen and hydroxide ions, and a detailed study of acid-base catalysis has been made by the same method by Bell and Evans (1966). 

Hydration and dehydration reactions have proved particularly convenient for studying catalysis by acids and bases over a wide range of structures and catalytic power. The results usually show a good correlation between acidic and basic catalytic constants and k ) and the of the catalyst, according to the usual Bronsted relations kjp = Ga qK /p) , ki, q = Gi, pjqKf, where p and q are statistical corrections. (These statistical corrections have not always been applied consistently, but the discrepancies thus introduced are not serious.) The information so far obtained is summarized in Table 3, and comments on the individual reactions follow. 

The catalytic constants for acids in aqueous solution correlate well with pK, and there is no apparent difference between uncharged and cation acids (carboxylic acids and pyridinium cations), though some steric inhibition is evident for 2,6-substituted pyridinium cations. The catalytic constants for bases behave somewhat more erratically, and it has been suggested by Gruen and MoTigue (1963b) that errors are intro-... 

The catalytic constants measured in 95% aqueous dioxan have been compared with piT-values in water. The twenty-four acids referred to in Table 3 are mainly carboxylic acids, but also include nitric acid, o-chloro-phenol and water. Two oximes show large positive deviations, and saccharin has considerably less catalytic activity than anticipated these substances have not been included in the correlation. A number of strong acids gave closely similar catalytic constants— HCl (3-05), HBr (2-30), CoHb.SOsH (2-30), MeSOsH (2-15), HCIO (1-25)—and the minor variations within this series are not in the expected order of acid strengths HCIO4 > HBr > HCl > ObHb. SO3H > MeSOsH. Presumably all these acids are converted in solution to the hydronium ion, the catalytic power of which is somewhat modified by ion-pairing with different anions in the solvent of low dielectric constant. The catalytic constants observed are consistent with the conventional value pJT = —1-74 for H36+. 

The speed V of an enzymatic reaction is governed by two important constants, charateristic of a given substrate the catalytic constant and the Michaelis constant... 

TURNOVER NUMBER CATALYTIC CONSTANT TURNOVER NUMBER CATALYTIC DOMAIN... 

The following diagram illustrates the reaction of acetylcholinesterase (E) with acetylcholine (S) to produce an acetylenzyme Intermediate (E ) with later hydrolysis of the Intermediate and regeneration of the enzyme.% Is calculated as shown in the diagram. The catalytic constant, kcat, refers to the overall decomposition of the enzyme Intermediate (E.S, E ). 

Values of a catalytic constant, 27 k computed from (6) are listed in Table V. It is obvious that the imidazole-substituted dodecylpoly-enimines are more than 100 times as effective as the simple imidazole28,29 molecule itself. The catalytic constant for the imidazole-dodecyl polymer in fact approaches that of the enzyme chymotrypsin. 

Comparing catalytic effects of different modified polyethylenimines on the decarboxylation of nitrobenzisoxazole carboxylate, we can discern several interesting features. Comparison of the 25% laurylated polymer in the quaternized and nonquaternized forms, A and D, respectively, in Table X, shows that the former is about three times more effective as a catalyst than the latter. For the quaternized polymer the first-order catalytic constant k2 and the second-order rate constant nk2IKM are greater and the binding of substrate (measured by XM ) is stronger. 

The very strong role played by the apolar environment is also evident in a comparison of 25% and 10% laurylated polethylenimines (A and C, respectively, in Table X). The catalytic constant fc2, reflecting the effect of polymer environment on the transition state, drops by a factor of 5 in the less apolar environment. 

What is the exact influence of water and organic molecules on the enzyme structure Could its effects on properties such as selectivity, affinity, binding constants, and catalytic constants be predictable by controlling the hydration/solvation state ... 

Bruice and Schmir (3) have shown that for a series of imidazole derivatives, klm depends on the base strength of the catalyst and since pKA is an approximate measure of base strength, the value of klm should increase with increase in pKA. Table I shows that this is indeed the case. Imidazole, pKA = 7.08, has a catalytic constant eight times larger than that of benzimidazole, pKA = 5.53. Bronsted and Guggenheim (2) have obtained a linear relationship between log k/ and pKA for a series of carboxylic acids in the pKA range of 2 to 5, where kB is the carboxvlate anion basic catalytic constant for the mutarotation of glucose and Ka is the acid dissociation constant of the acid. Our results for imidazole and benzimidazole fit fairly well into the Bronsted plot. 

COOH. The Michaelis constant was 6.5 mM, about 80 times that for the phosphate (or 40 times if one of the enantiomers was inert), and the catalytic constant was 230 times lower than for the phosphate. Similarly, phospholipase A2 cleaves the acyl group from 0-2 of 2,3-dihydroxypropylarsonic acid that is acylated on 0-2 and 0-3 (M. K. Jain, personal communication, 1995). 

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