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Esterases, tissue

Elestolol sulfate is a nonselective, ultrashort acting P-adrenoceptor blocker. It has no ISA and produces weak inhibition of the fast sodium channel. The dmg is under clinical investigation for supraventricular tachyarrhythmias, unstable angina, and acute MI. In humans, flestolol has hemodynamics and electrophysiologic effects similar to those of other P-adrenoceptor blockers. The pharmacokinetics of flestolol are similar to those of esmolol. It is 50 times more potent than esmolol and the elimination half-life is 7.2 min. Recovery from P-adrenoceptor blockade is 30—45 min after stopping iv infusions. The dmg is hydrolyzed by tissue esterases and no active metabohtes of flestolol have been identified (41). [Pg.119]

The differentiation of cells occurs concomitantly to modifications of wall components. The nature of the pectins of the walls changes under the action of enzymes, among which esterases, secreted between the apical meristematic cells and the more basal differentiated cells. The apposition of new layers of pectins with different compositions at the inner surface of the walls is another mechanism by which the cells adapt their immediate environment. Using the 2F4 antibody, we have observed, in plant suspensions as well as in tissues, a third mechanism involved in wall modification. Numerous invaginations of the... [Pg.143]

Immuno localizations of AE in sections of orange fruits are shown in Fig. 3. The most intensive depositions of acetyl esterase were found in the outermost parts of the peel (exocarp or outermost albedo and the flavedo) and in the segments (juice vesicles), although quite high levels of acetyl esterase were found in most other tissues as well. The acetyl esterase depositions were all intracellular. [Pg.728]

In the segments strong immunological deposition was found throughout the tissue. Again the results indicate a slight correlation of cell size and the amount of acetyl esterase. In the small cells in the periphery of the juice vesicles, acetyl esterase is clearly intracellular (Fig 3 D,E), whereas the acetyl esterase was found on the cell walls of the large inner juice cells. This... [Pg.728]

In lamella and core the strongest immunological depositions were found in the vascular bundles (Fig. 3 F), whereas acetyl esterase was present in moderate amounts in all other cells. No acetyl esterase was found in the outermost parts of the tissues, cuticula of epidermis, innermost cell layer of endocarp, outer walls of juice vesicles and outer cell layer of lamella. [Pg.730]

Some OP compounds induce delayed neurotoxic effects ("delayed neuropathy") after acute poisoning. This delayed neurotoxic action is independent of cholinesterase inhibition but related to phosphorylation of a specific esterasic enzyme in the nervous tissue, called "neurotoxic esterase" or "neuropathy target esterase" (NTE) (Johnson, 1982). NTE is present in the nervous tissue, liver lymphocytes, platelets, and other tissues, but its physiological function is unknown. There is a rather large inter-individual variation of lymphocyte and platelet NTE activity (Table 2). [Pg.4]

By use of model substrates and inhibitor studies, an esterase that is reactive in unbuffered sea water as well as in the disrupted algal tissue from C. taxifolia was identified which mediates cleavage of the acetyl residues of caulerpenyne (54) [121]. After complete deacetylation, oxytoxin 2 (64) appears as an unstable end-product. Due to the lack of an appropriate assay procedure for labile metabo-... [Pg.203]

Esterases form a wide family of enzymes that catalyze the hydrolysis of ester bonds. They are ubiquitously expressed in all tissues including the intestine, and are found in both microsomal and cytosolic fractions. Prueksaritonont et al. [6] have studied the metabolism of both p-nitrophenol acetate and acetylsalicylic acid by esterases from human intestinal microsomal and cytosolic systems, and the activity values were 2.76 pmol min-1 mg-1 and 0.96 nmol min-1 mg-1, respectively. Thus, the activity for the hydrolysis of p-nitrophenol acetate in human intestine approaches that in the liver. [Pg.315]

Irinotecan is a prodmg, and hydrolysis of irinotecan by the high-affinity carboxyl-esterase-2 enzyme in many normal tissues and tumors is responsible for activa-... [Pg.292]

It was reported that the distribution and activities of esterases that catalyze pyrethroid metabolism using several human and rat tissues, including small intestine, liver, and serum, were examined [30]. The major esterase in human intestine was hCE2. //c/n.v-Permethrin was effectively hydrolyzed by pooled human intestinal microsomes (five individuals), while deltamethrin and bioresmethrin were not. This result correlated well with the substrate specificity of recombinant hCE2. In contrast, pooled rat intestinal microsomes (five animals) hydrolyzed trans-permethrin 4.5 times slower than the human intestinal microsomes. Furthermore, pooled samples of cytosol from human or rat liver were ca. half as hydrolytically active as the corresponding microsome fraction toward pyrethroids however, the cytosolic fractions had significant amounts (ca. 40%) of the total hydrolytic activity. Moreover, a sixfold interindividual variation in hCEl protein expression in human hepatic cytosols was observed. [Pg.124]

Both /nmv-permethrin and bioresmethrin were effectively cleaved by rat serum CES on the other hand, deltamethrin, esfenvalerate, a-cypermethrin, and cis-permethrin were slowly hydrolyzed. These results suggest that PBPK models of some pyrethroids may require the parameter of esterase activity to calculate the concentrations in the intestinal tract, liver, and serum if it is shown that the compounds in the model are appreciably hydrolyzed within these tissues. Such data for human and animal tissues will help to improve the accuracy of extrapolation between species (e.g., rats to humans) and thus enable better predictions of tissue and blood concentrations in humans following exposure to pyrethroids [30]. [Pg.131]

Thus a distinction was provided between simple esterases, such as fiver esterase, which catalysed the hydrolysis of simple aliphatic esters but were ineffective towards choline esters. The term 1 cholinesterase was extended to other enzymes, present in blood sera and erythrocytes of other animals, including man, and in nervous tissue, which catalysed the hydrolysis of acetylcholine. It was assumed that only one enzyme was involved until Alles and Hawes2 found that the enzyme present in human erythrocytes readily catalysed the hydrolysis of acetylcholine, but was inactive towards butyrylcholine. Human-serum enzyme, on the other hand, hydrolyses butyrylcholine more rapidly than acetylcholine. The erythrocyte enzyme is sometimes called true cholinesterase, whereas the serum enzyme is sometimes called pseudo-cholinesterase. Stedman,3 however, prefers the names a-cholinesterase for the enzyme more active towards acetylcholine, and / -cholinesterase for the one preferentially hydrolysing butyrylcholine. Enzymes of the first type play a fundamental part in acetylcholine metabolism in vivo. The function of the second type in vivo is obscure. Not everyone agrees with the designation suggested by Stedman. It must also be stressed that enzymes of one type from different species are not always identical in every respect.4 Furthermore,... [Pg.72]

In addition, they noted that in tissue cultures the growth of the malignant cells (lymphoblasts) of a mouse lymphosarcoma is inhibited by E 600 in a concentration which inhibits the esterase... [Pg.214]

Fig. 10 TLC plate showing degradation of (R)- and (S)-japonilure (upper spots) by esterases from the legs (Leg) and antennae (Ant) of the Japanese beetle. The corresponding hydroxy-acids appear as lower bands. Note the slower degradation of the behavioral antagonist, (S)-japonilure, by sensillar esterase(s) from the antennae. Neither (R)- nor (S)-japonilure is degraded in control experiments (data not shown) under the same conditions, i.e., with the compounds incubated in buffer without Japanese beetle tissue extracts... Fig. 10 TLC plate showing degradation of (R)- and (S)-japonilure (upper spots) by esterases from the legs (Leg) and antennae (Ant) of the Japanese beetle. The corresponding hydroxy-acids appear as lower bands. Note the slower degradation of the behavioral antagonist, (S)-japonilure, by sensillar esterase(s) from the antennae. Neither (R)- nor (S)-japonilure is degraded in control experiments (data not shown) under the same conditions, i.e., with the compounds incubated in buffer without Japanese beetle tissue extracts...
Metabolism Glucuronidation N-demethylation Ester hydrolysis to morphine Glucuronidation demethylation (CYP2D6) Ester hydrolysis N-demethylation N-Dealkylation, then hydroxylation N-Demethylation Plasma and tissue esterases... [Pg.226]


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See also in sourсe #XX -- [ Pg.49 ]




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