Substrate–inhibitor specificity of cholinesterase and monoamine oxydase from optic ganglia of the pacific squid <Emphasis Type="Italic">Todarodes pacificus</Emphasis> and commander squid <Emphasis Type="Italic">Berryteuthis magister</Emphasis>

A comparative analysis of enzymological characteristics of cholinesterase (ChE) and monoamine oxydase (MAO) from the optic ganglia was performed in the Pacific squid Todarodes pacificus and Commander squid Berryteuthis magister caught in their four habitats across the Pacific Northwest. A substrate–inhibitor analysis revealed a homogeneity of T. pacificus and B. magister ChE preparations as well as homogeneity of T. pacificus vs. heterogeneity of B. magister MAO preparations. In case of thiocholine derivatives, the rate of hydrolysis induced by T. pacificus ChE was practically independent of the structure of the acyl group, whereas in case of B. magister ChE it was found to decrease in this substrate series. It is only T. pacificus MAO that was found to be able to deaminate also a diaminooxydase substrate histamine. ChE activity was higher in T. pacificus than in B. magister for the whole substrate series, while for MAO the same activity pattern was observed for tyramine, tryptamine and serotonin. In both squids, the sensitivity of ChE to organophosphorus inhibitors containing the dimethylbutyl group was by several orders of magnitude higher than that in mammals. The sensitivity of ChE to the siloxane reversible inhibitors was lower in T. pacificus ChE and much lower in B. magister than in mammals.     

How thionphosphonates inhibit activity of different cholinesterases

Analysis of mechanism of reversible inhibition of human erythrocyte acetylcholinesterase (AChE), of horse serum cholinesterase (ChE), and ChE of optical ganglia tissue of individuals of the Commander squid Berryleuthis magister from various habitat zones was studied under effect of thionphosphonates (P=S), derivatives of piperidine, morpholine, perhydroazepine as well as several heterocyclic model compounds. Data of comparative inhibitory specificity have allowed us to suggest that thionphosphonates are sorbed in the area of cholinesterase esterase center through the phosphoryl part of the inhibitor molecule, rather than through its heterocyclic grouping. An advantage in the antienzyme efficiency of thionphosphonates (P=S) over phosphonates (P=O) is revealed. Effect of the ion strength is used for analysis of contribution of the hydrophobic—hydrophilic interaction in the enzyme—inhibitor system.     

Comparative Study of Reversible Organofluorine Ammonium Inhibitors of Cholinesterases of Different Animals

A group of organofluorine ammonium compounds, trimethyltrifluoromethylammonium, diethylmethyltrifluoromethylammonium, hexa(difluoromethylene)-bis(trimethylammonium), their non-substituted analogs as well as bis-onium organosilicone, phenyliodonium, and triphenylphosphonium derivatives were tested as reversible inhibitors of acetylcholinesterase of human erythrocytes, butyrylcholinesterase of horse blood serum, cholinesterase of brain of the frog Rana temporaria and cholinesterases of optic ganglion of the Pacific squid Todarodes pacificus. By the method of molecular mechanics, differences were revealed in conformational mobility of interonium chain and in geometric parameters of the studied compounds. It was shown that introduction of fluorine atoms into the inhibitor molecule affected only their interaction with the Pacific squid cholinesterase. It was possible to separate effects of the onium atom nature and of the interonium chain structure in the inhibitor molecule on the anticholinesterase potency.     

Interaction of membrane-bound and solubilized acetylcholinesterase from human and bovine erythrocytes with organophosphorus inhibitors

Differences are found between the membrane-bound and soluble acetylcholinesterases of human and bovine erythrocytes when the enzyme interacts with organophosphoric inhibitors in the presence of acetylc choline and galantamine, a reverse inhibitor of acetylcholinesterase. In most cases prevention of inhibition of the soluble enzyme activity necessitates a higher (2-3 times higher) concentration of the protecting agent than protection of the membrane-bound enzyme. Concentrations of acetylcholine and galantamine providing a 50% protection of the enzyme did not practically depend on the strength of the anticholinesterase action of organophosphoric inhibitors.