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G M Grigor'eva

Publications and source records attributed to G M Grigor'eva.

14 recordsLinked to original sources
PubMed1986

[Selectivity of the effect on cholinesterase of stereoisomers of thiophosphonates with asymmetrical phosphorus atoms].

The inhibitory action of stereoisomers of organophosphorous compounds with asymmetric phosphorous atom, (CH3)2CHO(CH3)P(O)SCH2CH2SC2H5 and (CH3)2CHO(CH3). .P(O)(CH2)3CH3, on acetylcholinesterase from nervous ganglia of cockroach Periplaneta americana and bovine erythrocytes as well as on horse serum butyrylcholinesterase was studied at pH 7.5 and 25 degrees C. It was found that the interaction of the inhibitors with cholinesterases has a complex type and includes reversible and irreversible stages resulting in the formation of noncovalent enzyme-inhibitor complex and phosphorylation of the enzyme, respectively. The affinity constants Ka, phosphorylation rate-constants kp, bimolecular reaction constants kII for enzyme inhibition, as well as the dissociation constants Ki, r for unproductive sorbtion of inhibitor were determined. Much greater selectivity in the action of (-)isomers of both thiophosphonates, as compared to (+)isomers, on acetylcholinesterases were observed, the effect being most pronounced for the cockroach enzyme. On the other hand, no marked differences were discerned between isomers in their binding to butyrylcholinesterase. The stereospecificity of the enzymes under study at different stages of interaction with the inhibitors was characterized.

Cholinesterase Inhibitors↗
PubMed1980

[Propionylcholinesterases from the brain of Mollusca Interaction with substrates and inhibitors].

The kinetics of hydrolysis of choline esters under the action of propyonylcholinesterases (acylcholine--acylhydrolase, EC 3.1.1.8) from the brain of some Gastropoda--Lymnaea stagnalis, Murex frunculus and Rapana thomasiana were studied. It was shown that the propyonylcholinesterases under study differ from typical cholinesterases of vertebrates. Their catalytic action is characterized by a high rate of hydrolysis of propyonylcholine (PCh) and butyrylcholine (BCh), inhibition of activity by high concentrations of the substrates and the inability to catalyze the hydrolysis of benzoyl choline and acetyl-beta-methylcholine (AMCh) with the exception of a low rate of AMCh hydrolysis induced by propyonylcholinesterase of L. stagnalis. The correlation of the hydrolysis rates of PCh, BCh and acetylcholine (ACh) is different. A comparison of the kinetic parameters of Km, V and V/Km for the enzymatic hydrolysis of substrates allowed to establish differences between various propyonylcholinesterases coupled with the values of the kinetic constants for initial and final steps of hydrolysis. Propyonylcholinesterase from M. trunculus is a "proper" propyonylcholinesterase, since PCh is the best substrate for it, both at the stage of the enzyme-substrate complex formation and upon its catalytic conversion. The most preferable substrate for the L. stagnalis enzyme at the stage of the enzyme-substrate complex formation is ACh, that for the R. thomasiana enzyme--BCh. The Kss values for the substrate inhibition of propyonylcholinesterase activity were determined. The enzyme from M. trunculus is characterized by the lowest Kss values for BCh, PCh and ACh. The propyonylcholinesterase activity is inhibited by eserine and organophosphorus inhibitors (OPI). The values of bimolecular constants (kappa II) of the rate of interaction with the cationic OPI, methylsulfomethylate (O-ethyl-S-(beta-ethylmercaptoethyl) methylthiophosphonate (Gd-42) for all propyonylcholinesterases greatly exceed those for the corresponding cation-free analog of Gd-7; however, the kappa IIGd-42/kappa IIGd-7 ratio is different. The selectivity towards the acyl radical structure and the split-off moiety of the OPI molecule is also different, i. e. the highest kappa II for L. stagnalis propyonylcholinesterase was determined with Gd-42, for the M. trunculus enzyme--with methylsulfomethylate O,O-diethyl-S-(beta-ethylmercaptoethyl) thiophosphate, for the R. thomasiana enzyme--with iodomethylate O,O-diethyl-S-(beta-cyclohexyldimethylaminoethyl) thiophosphate. Data on OPI suggest that the propyonylcholinesterases under study differ in some features in the structure of anionic and esterase moieties of their active surface.

Animals↗
PubMedDate not supplied

[Solar elements in the control of photon irradiation parameters in radiotherapy].

A study was made of the dosimetric characteristics of semiconductor detectors (on the basis of silicon with the p-i-n structure) and combined detectors (scintillation crystals based on CsJ/Tl combined with silicon detectors). The spectral characteristics of semiconductor and combined detectors are described. The results of levelling of hardness dependence by filtration and combination of detectors are presented; their isotropism is reviewed.

Humans↗
PubMedDate not supplied

[A comparative study of the interaction of the cholinesterase from the brain of the cabbage fly, the acetylcholinesterase from bovine erythrocytes and the butyrylcholinesterase from horse blood serum with organophosphorus inhibitors].

Studies have been made of the effect of several organophosphorus inhibitors, R1(R2)P(O) . SCH2CH2SR and R1(R2)P(O)SCH2CH2SRR . -O4SCH3 (or -I), which differ by the structure of split (R, P) and phosphoryl (R1, R2) parts of the molecule, on cholinesterase (ChE) from the brain of the fly Delia brassicae, acetylcholinesterase (AChE) of the bovine erythrocytes and butyrylcholinesterase (BuChE) from the blood serum of the horse. For fly ChE, higher values of a constant (kII) of the inhibition rate (at pH 7.5 and temperature 25 degrees C) were obtained both with thiophosphates and with thiophosphonates. This finding reveals higher reactivity of the active centre of this enzyme, as well as significantly lower selectivity of the latter to the structure of organophosphorus inhibitors. The data obtained suggest the existence of differences in the size of hydrophobic regions of anionic and esterase parts of the active centre in ChE of the fly and AChE of mammals, as well as the existence of some similarity between ChE of the fly and BuChE.

Acetylcholinesterase↗
PubMedDate not supplied

[Acetylcholinesterase from the electric organ of the ray Torpedo marmorata].

Studies have been made on substrate specificity of acetylcholinesterase (AChE;EC 3-1-1-7) from the electric organ of the ray T. marmorata with respect of choline and thiocholine esters, as well as on the effect of pH, salts and organophosphorus inhibitors (OPI) on the activity of the enzyme. Acetylcholine (ACh), propionycholine (PrCh) acetyl-beta-methylcholine (MeCh), acetylthiocholine ((ATCh) and propionylthiocholine (PrTCh) were hydrolyzed by the enzyme studied at the following relative rates-100: 28.8: 18.3: 87.2: 18.9 correspondingly. In all the cases, inhibition of the enzyme by high concentrations of the substrate was observed. As compared to other AChE, the enzyme from T. marmorata exhibits the highest affinity to ACh. For all the substrates studied, pH dependence of AChE activity followed the curve with maximum 7.5 for ACh and PrCh, 8.0-8.5 for ATCh and MeCh and 7.5-8.5 for PrTCh. Various salts (MgCl2), KCl, NaCl, NaBr, KI) increased AChE activity, the increase being the highest with MgCl2 (3.3 times) and NaCl (2.5X). Biomolecular rate constants ((k) II) for the interaction of AChE investigated with OPI containing cationic group-methylsulfomethylates, O-ethyl-S-(beta-ethylmercapto) ethylmethylthiophosphonate and O,O-diethyl-S-(beta-ethylmercapto) ethylthiophosphate, as well as methyl iodide O,O-disopropyl-S-(beta-phenylmethylamino) ethylphosphate-were significantly higher as compared with k(II) values for corresponding compounds without the cation. The value of k(II) sharply decreased with the increase in the size of the acyl radicals at phosphorus atom in the molecule of OPI.

Acetylcholine↗