Acetylcholinesterases (AChE, EC 3.1.1.7) are serine hydrolases, whose primary function in animals is the specific hydrolysis of the neurotransmitter acetylcholine at cholinergic synapses. As such they are target of organophosphate and carbamate insecticides, that modify and inactivate the enzyme, and finally lead to paralysis and death. Past studies on mollusks cephalopods and bivalves reported the presence of AChE forms with high substrate specificity, high catalytic efficiency, and low sensitivity to diisopropylfluorophosphate (DFP). In the most widely used sentinel species in pollution monitoring studies of the marine environment, the Mediterranean mussel Mytilus galloprovincialis, the AChE form associated to membrane does not undergo inhibition to DFP. The present study investigate Ace gene in three different organs of M. galloprovincialis: pedal and cerebral ganglia, gills and adductor muscle. The entire Ace gene was amplified in three overlapping fragments. Sequence analysis showed an open reading frame encoding a protein of 624 amino acids with an high homology of 50% with Ace of Loligo opalescens and less as 20–41% with others. The general structure of AChE seems conserved in the mussel AChE: three amino acid residues on the catalytic domain as well as Trp which binds the quaternary ammonium of Ach. The deduced amino acids sequence showed also in the acyl pocket the presence of a polar amino acid [N327] in a strategic position commonly occupied in the sensitive forms by a non polar one [F(288) in Torpedo]. Such substitution might be responsible of the high substrate specificity toward ASCh of mussel AChE, the absence of hydrolysis of BSCh and the resistance to DFP. The newly obtained sequence of M. galloprovincialis AChE will open to the possibility of studying the evolution and geographic origin of different, resistant and not resistant, AChE alleles.
Organophosphate-resistant acetylcholinesterase in Mytilus galloprovincialis: identification of a resistance Ace gene in cerebral ganglion, gills and adductor muscle
ROMANI, Rita;ROSI, Gabriella;
2008
Abstract
Acetylcholinesterases (AChE, EC 3.1.1.7) are serine hydrolases, whose primary function in animals is the specific hydrolysis of the neurotransmitter acetylcholine at cholinergic synapses. As such they are target of organophosphate and carbamate insecticides, that modify and inactivate the enzyme, and finally lead to paralysis and death. Past studies on mollusks cephalopods and bivalves reported the presence of AChE forms with high substrate specificity, high catalytic efficiency, and low sensitivity to diisopropylfluorophosphate (DFP). In the most widely used sentinel species in pollution monitoring studies of the marine environment, the Mediterranean mussel Mytilus galloprovincialis, the AChE form associated to membrane does not undergo inhibition to DFP. The present study investigate Ace gene in three different organs of M. galloprovincialis: pedal and cerebral ganglia, gills and adductor muscle. The entire Ace gene was amplified in three overlapping fragments. Sequence analysis showed an open reading frame encoding a protein of 624 amino acids with an high homology of 50% with Ace of Loligo opalescens and less as 20–41% with others. The general structure of AChE seems conserved in the mussel AChE: three amino acid residues on the catalytic domain as well as Trp which binds the quaternary ammonium of Ach. The deduced amino acids sequence showed also in the acyl pocket the presence of a polar amino acid [N327] in a strategic position commonly occupied in the sensitive forms by a non polar one [F(288) in Torpedo]. Such substitution might be responsible of the high substrate specificity toward ASCh of mussel AChE, the absence of hydrolysis of BSCh and the resistance to DFP. The newly obtained sequence of M. galloprovincialis AChE will open to the possibility of studying the evolution and geographic origin of different, resistant and not resistant, AChE alleles.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
