Two invertebrate acetylcholinesterases show activation followed by inhibition with substrate concentration.
In vertebrates there are two cholinesterases, with differences in catalytic behaviour with respect to substrate concentration: butyrylcholinesterase displays an increased activity at low substrate concentrations, whereas acetylcholinesterase displays inhibition by excess substrate. In two invertebrates, Drosophila melanogaster and Caenorhabditis elegans, we found cholinesterases that showed both kinetic complexities: substrate activation at low substrate concentrations followed by inhibition at higher concentrations. These triphasic kinetics can be explained by the presence of two enzymes with different kinetic behaviours or more probably by the existence of a single enzyme regulated by the substrate concentration.
Marcel
V
V
Laboratoire d'entomologie, Université Paul Sabatier, 31062 Toulouse, France.
Palacios
L G
LG
Pertuy
C
C
Masson
P
P
Fournier
D
D
D000110:Acetylcholinesterase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D017173:Caenorhabditis elegans / Q000201:enzymology*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D018076:DNA, Complementary; D004331:Drosophila melanogaster / Q000201:enzymology*; D004789:Enzyme Activation; D007700:Kinetics; D013379:Substrate Specificity
D002800:Cholinesterase Inhibitors; D018076:DNA, Complementary; D000110:Acetylcholinesterase