Comparison of two reaction schemes for the hydrolysis of acetylthiocholine by butyrylcholinesterase (CROSBI ID 492813)
Prilog sa skupa u zborniku | izvorni znanstveni rad | međunarodna recenzija
Podaci o odgovornosti
Simeon-Rudolf, Vera ; Šinko, Goran ; Štuglin, Anita ; Stojan, Jure ; Goličnik, Marko ; Reiner, Elsa
engleski
Comparison of two reaction schemes for the hydrolysis of acetylthiocholine by butyrylcholinesterase
Catalytic parameters calculated from the schemes derived by Webb (Model A) and by Stojan (Model B) were compared for the hydrolysis of acetylthiocholine (ATCh) by purified horse serum butyrylcholinesterase (BChE) (measured by conventional and stopped-flow techniques). In Model A the acetylated enzyme is omitted from the scheme, while in Model B the Michaelis complex is omitted. The enzyme-substrate dissociation constants Ks and Kss in Model A were 0.25 and 2.0 mM (conv. tech.) and 0.17 and 6.3 mM (stopped-flow tech.). These were attributed to binding of ATCh to the catalytic and peripheral site of BChE. The constants K1 and K2 in Model B (stopped-flow tech.) were 0.223 and >1000 mM. These are attributed to binding of ATCh to an unidentified site in the free enzyme and to the peripheral site in the acetylated enzyme. As the Ks and K1 values are almost the same, both constants are likely to refer to the same enzyme-substrate complex. The constants Kss and K2 are very different ; they are both attributed to peripheral binding of ATCh, but they obviously refer to different complexes. Both models postulate that peripheral binding of a substrate affects rate constants of substrate hydrolysis ; this also follows from the evaluated constants for ATCh hydrolysis.
butyrylcholinesterase; acetylthiocholine; mechanism
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Podaci o prilogu
701-703-x.
2004.
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objavljeno
1841840750
Podaci o matičnoj publikaciji
Cholinergic mechanisms : Function and Dysfunction : Proceedings of the XIth ISCM
Fisher, Abraham ; Silman, Israel ; Soreq, Hermona ; Anglister, Lili ; Michaelson, Daniel M.
London : Delhi: Francis & Taylor
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Nepoznat skup
predavanje
29.02.1904-29.02.2096