Effect of pH, temperature and ionic strength on the aging of phosphonylated cholinesterases
article
The rates of aging of cycloheptyl methylphosphonylated bovine erythrocyte acetylcholinesterase (acetylcholine acetyl hydrolase, EC 3.1.1.7) and horse serum butyrylcholinesterase (acylcholine acyl hydrolase, EC 3.1.1.8) were investigated as function of pH, temperature and ionic strength. From the pH rate profiles at 25°C and I = 0.100, it was concluded that a protonated group with pK 5.84 is involved in the aging of the phosphonylated acetylcholinesterase and a protonated group with pK 7.35 in the aging of the phosphonylated butyrylcholinesterase. The influence of temperature and ionic strength on the pH rate profile of aging of the phosphonylated acetylcholinesterase suggests the participation of an undissociated carboxyl group of the enzyme catalyzing the formation of a carbonium ion in the rate determining step. The mechanism of aging of phosphonylated butyrylcholinesterase was more complicated.
Topics
TNO Identifier
227582
ISSN
00063002
Source
Biochimica et Biophysica Acta (BBA) - Enzymology, 334(1), pp. 146-155.
Pages
146-155
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