Inhibition constant table

Common inhibitors include stable radicals (Section 5.3.1), oxygen (5.3.2), certain monomers (5.3.3), phenols (5.3.4), quinones (5.3.5), phenothiazine (5.3.6), nitro and nitroso-compounds (5.3.7) and certain transition metal salts (5.3.8). Some inhibition constants (kjkp) are provided in Table 5.6. Absolute rate constants (kj) for the reactions of these species with simple carbon-centered radicals arc summarized in Tabic 5.7. 

Results of inhibition studies with nojirimycin and its analogs published up to 1988, and additional data from the author s laboratory, are summarized in Table VI. It should be noted that the inhibition constants are given in pM instead of mM (as in Tables II - V). Data for glycosylamines are included, in order to facilitate an estimation of the effects caused by the different positions of the basic group in the two types of basic sugar derivative. Not included are the data of Reese and coworkers and of Grover and Cushley on nojirimycin, because these authors were apparently unaware of the slow and only partial dissociation of the nojirimycin hydrogensulfite adduct which had been used instead of free nojirimycin. 

In the first group of studies, involving kinetic inhibition studies, comparisons of the uilibrium (K ), phosphorylation (IC), and inhibition constant (K.) for the inhibition of electric eel and human erythrocyte AChE by ANTX-A(S) and DFP were done (Table II). From Table II it is seen that ANTX- A(S) has a higher affinity for human erythrocyte AChE (K =0.253 fiM) than electric eel AChE (K j=3.67 aM). AN DC-A(S) also shows greater affinity for AChE than DFP (K =300 fiM). And finally the bimolecular rate constant, Kj, which indicates the overall rate of reaction, shows AChE is more sensitive toward inhibition by ANTX-A(S) (Kj=1.36 pM- min- ) than DFP (K, = 0.033 /iM- min ). These studies add information to the comparative activity of ANTX-A(S) and other irreversible AChE inhibitors but do not show the site of inhibition. 

Table III. Inhibition Constants for Derivative Brevetoxins Derived from the Cheng-Pmsotf Equation ...

The in vitro bioassays allowed to determine the inhibition constant of D-fructose transport by the CHO cells. This measure is carried out by competition with radioactive D-fructose. The study put in evidence that pentose-OZT derivatives are not recognized by the protein transporter. Only the ketohexose-OZT derivatives expressed some inhibition of GLUT5. These inhibition constants showed to be much effective with L-Sor derivatives than with D-Fru derivatives and even better than D-fructose itself (Kt = 15.5 mM) (Table 2). 

In initial studies with /3-CD it was noted that values of ka vary in inverse proportion to the inhibition constant, Kt, suggesting that PI is bound in the CD cavity in the transition state (Tee and Hoeven, 1989). Therefore, the Pi-mediated reaction is more reasonably viewed as being between the ester and the PI-CD complex. The third-order processes in (21) and (24) are kinetically equivalent (k2 = k.JKs = kJKy), and so kb values are easily found from k.t. Such values of kb show some variation with structure but they are quite similar for different Pis and not very different from k2 for the reaction of the CD with pNPA For example, for pNPA reacting with 15 different alcohol /3-CD complexes values of kb span the range 10-95 m 1 s l (Table A5.14), close to k2 = 83m-1s-1 for the reaction of pNPA with /3-CD alone. Similar behaviour was observed for other Pis (Table A5.14) and for aCD (Table A5.13), for which k2 = 26 m-1 s 1. 

Figure 4.11 Effect of inhibition of enzyme 2 by cofactor A and of enzyme 1 by cofactor B (i.e., product inhibition) on the concentration of B in the basic system when operated as a fed-batch reactor. For the central and right panels the inhibition constants are indicated on top of each section. In the left panel, inhibition by products was not considered, and—indicates that the parameter is not applicable. Data presented in the left panel are taken from Figure 4.4. The values used for all other parameters ares given in Table 4.1, set I.

Kinetics of O-Methylaiion. The steady state kinetic analysis of these enzymes (41,42) was consistent with a sequential ordered reaction mechanism, in which 5-adenosyl-L-methionine and 5-adenosyl-L-homocysteine were leading reaction partners and included an abortive EQB complex. Furthermore, all the methyltransferases studied exhibited competitive patterns between 5-adenosyl-L-methionine and its product, whereas the other patterns were either noncompetitive or uncompetitive. Whereas the 6-methylating enzyme was severely inhibited by its respective flavonoid substrate at concentrations close to Km, the other enzymes were less affected. The low inhibition constants of 5-adenosyl-L-homocysteine (Table I) suggests that earlier enzymes of the pathway may regulate the rate of synthesis of the final products. 

There are two major factors to be considered in assessing the contribution of potential oxidants for S(IV) to the net aqueous-phase oxidation. The first is the aqueous-phase concentration of the species, and the second is the reaction kinetics, that is, the rate constant and its pH and temperature dependencies. As a first approximation to the aqueous-phase concentrations, Henry s law constants (Table 8.1) can be applied. It must be noted, however, that as discussed earlier for S(IV) this approach may lead to low estimates if complex formation occurs in solution. On the other hand, high estimates may result if equilibrium between the gas and liquid phases is not established, for example, if an organic film inhibits the gas-to-liquid transfer (see Section 9.C.2). 

Table 2 Inhibition Constants and Fold Induction of CYP3A4 for the Principal Constituents of St. John s Wort on Human CYP Activities...

This type of rate law is employed in the global DOC kinetic model given in Table II (cf. reaction R5). A typical evolution of the outlet NOx concentration in the course of a slow temperature ramp is shown in Fig. 14. From this type of experiment, the selectivity and inhibition constants A(7) are evaluated, considering exponential temperature dependence, Eq. (36). Again, simpler HC + 02 + NO reaction mixtures with single hydrocarbon are examined first, followed by more complex inlet gas compositions. 

The dependence of the kinetic constants (Table I) upon the concentration of Ca2t, pH, and ionic strength is not the same for all the synthetic substrates shown on Table I. In general, however, with all these substrates the maximal velocities are achieved between pH 9 and 11, maximal affinity for substrate occurs between pH 7.5 and 8.5 (Fig. 4), and inhibition of enzymic activity is observed with NaCl concentrations greater than 0.1 N. Similar dependence upon these parameters is seen when activities are measured with DNA and RNA (3). 

Crude estimates of the affinities of the enzyme for other compounds have been made by study of their capacity to inhibit hydrolysis of PPi. If the observed inhibition is assumed to be competitive, a simplified kinetic treatment yields the inhibition constants (Ki" values) listed in Table VI (54). The data indicate that several of the compounds whose hydrolysis is not catalyzed (Section III,D) are nevertheless bound weakly to the enzyme (e.g., ADP, methylene-bis-phosphonate). There is also very weak binding of Pi( the product of the enzymic reaction [Eq. 

Table 3.2 experimentally determined inhibition of ADH. The inhibition constant an< enantiomeric excess ee of carbinol formation for three ketones. Competitive inhibition of ADH was observed for 1 and 3, whereas irreversible inhibition by alkylation occurred for 2. 

The enantiomeric excess (ee) of carbinol formation was determined for the three /9-keto esters 1-3. Their inhibition constants for ADH are given in Table 3.2. 

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