Naslov
Comparison of two reaction schemes for the hydrolysis of acetylthiocholine by butyrylcholinesterase

Autori
Simeon-Rudolf, Vera ; Šinko, Goran ; Štuglin, Anita ; Stojan, Jure ; Goličnik, Marko ; Reiner, Elsa

Vrsta, podvrsta i kategorija rada
Radovi u zbornicima skupova, cjeloviti rad (in extenso), znanstveni

Izvornik
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, 2004, 701-703

ISBN
1841840750

Skup
XIth International Symposium on Cholinergic Mechanisms Function and Dysfunction and 2nd Misrahi Symposium on Neurobiology

Mjesto i datum
St. Moritz, Švicarska, 05.05.2002. - 09.05.2002

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
butyrylcholinesterase; acetylthiocholine; mechanism

Sažetak
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.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA