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Choline acetylthio

The most outstanding example illustrating this strategy came from the team of Alain Friboulet and Daniel Thomas, who produced anti-idiotype antibodies against a monoclonal antibody AE2 that was a competitive inhibitor of acetylcholine esterase. One of the selected antibodies, 9A8, catalyzes the hydrolysis of acetylthio-choline with a pseudo first-order rate constant /feat = 81 and a factor of acceleration of 4.2 x 10 . These remarkable parameters, which are only two orders of magnitude lower when compared to those of the enzyme, make abzyme 9A8 the most powerful abzyme known until now. [Pg.346]

Quantification of Cholinesterase Activity in Serum Adjustthe temperature of 3 ml of dithiobisnitrobenz-oic acid solution to 25°, add 20 ll1 of the serum sample and 0.1 ml of a 5% solution of acetylthio-choline iodide, mix well, and record the absorbance of a 1-cm layer at 405 nm at 30-second intervals over a period of 2 minutes. If the change in absorbance exceeds 0.2 in 30 seconds, dilute the sample 1 in 10 with normal saline and repeat the measurements (the readings must then be multiplied by 10). The concentration of cholinesterase is calculated as follows ... [Pg.23]

Acetylcholinesterase is mechanistically related to serine proteases and involves acylation of Ser and contains the catalytic triad Ser -His -Glu. Precise data for acetylation by the natural substrate acetylcholine is difficult to obtain due to lack of a convenient assay method, so the mechanistically equivalent surrogate acetylthio-choline has frequently been used to probe mechanistic aspects of this enzyme [15]. To explore proton transfer reactions that accompany acetylation by this substrate, solvent isotope effect measurements and proton inventories on k /Km have been conducted [16, 17]. The isotope effects are near unity and the proton inventories bowed-upwards, suggesting that the transition state for kjKm is a virtual transi-... [Pg.1460]

In 1990, we reported [ 166] that CPT-11 inhibits acetylcholinesterase activity. In the paper, the rate of thiocholine (TCh) production from acetylthio-choline iodide (ATChl) by acetylcholinesterase was analyzed with Line-weaver-Burk plots (Figure 2.3). This kinetic analysis indicated that CPT-11 noncompetitively inhibited acetylcholinesterase. In this case, the apparent Michaelis constant (Km) and inhibition constant (Ki) ranged from 63 to 68 yUM and from 0.221 to 0.300 /iM, respectively (Table 2.3). The same analysis revealed that the Ki value of physostigmine (a potent acetylcholinesterase... [Pg.91]


See other pages where Choline acetylthio is mentioned: [Pg.417]    [Pg.64]   
See also in sourсe #XX -- [ Pg.400 ]




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