Effects of Ni(2+), Co(2+), and Mn(2+) on desensitized butyrylcholinesterase prepared from human serum.
Human serum butyrylcholinesterase (BChE) has been converted into a stable but less active desensitized form when heated at 45 degrees C for 24 h. The desensitized BChE follows Michaelis-Menten kinetics, whereas native enzyme exhibits slightly negative cooperativity with respect to butyrylthiocholine binding. In this study, we investigated the effects of Ni2+, Co2+, and Mn2+ on the desensitized BChE. It is found that all three ions were noncompetitive inhibitors of the desensitized BChE, and Ki values have been determined as 7.816 +/- 1.060 mM, 48.722 +/- 4.635 mM, and 84.795 +/- 5.249 mM for Ni2+, Co2+, and Mn2+, respectively. In our previous study, these ions were linear mixed-type inhibitors of the native BChE. This finding confirms that desensitized BChE changes to a different conformation than native BChE. From the comparison of Ki values of the trace elements, it can be said that Ni2+ is a more effective inhibitor of the desensitized BChE than Co2+ and Mn2+.
Cengiz
Dogan
D
Department of Biochemistry, Hacettepe University, Faculty of Medicine, 06100 Ankara, Turkey.
Cokugras
A Nese
AN
Tezcan
E Ferhan
EF
D002091:Butyrylcholinesterase / Q000097:blood* / Q000378:metabolism*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology*; D004795:Enzyme Stability; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology*; D009532:Nickel / Q000494:pharmacology*; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation
D002800:Cholinesterase Inhibitors; D003035:Cobalt; D008345:Manganese; D009532:Nickel; D002091:Butyrylcholinesterase