Cholinesterases from Plant Tissues: II. Inhibition of Bean Cholinesterase by 2-Isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine Carboxylate Methyl Chloride (AMO-1618)

An enzyme inhibition-based lab-in-a-syringe device for point-of-need determination of pesticides

An enzyme inhibition-based lab-in-a-syringe (EI-LIS) device was developed by integrating a 1-naphthol-linked bi-enzymatic reaction (sensor core) into the LIS (sensor device) for point-of-need monitoring of pesticide residues.

Efforts toward treatments against aging of organophosphorus-inhibited acetylcholinesterase

Aging is a dealkylation reaction of organophosphorus (OP)-inhibited acetylcholinesterase (AChE). Despite many studies to date, aged AChE cannot be reactivated directly by traditional pyridinium oximes. This review summarizes strategies that are potentially valuable in the treatment against aging in OP poisoning. Among them, retardation of aging seeks to lower the rate of aging through the use of AChE effectors. These drugs should be administered before AChE is completely aged. For postaging treatment, realkylation of aged AChE by appropriate alkylators may pave the way for oxime treatment by neutralizing the oxyanion at the active site of aged AChE. The other two strategies, upregulation of AChE expression and introduction of exogenous AChE, cannot resurrect aged AChE but may compensate for lowered active AChE levels by in situ production or external introduction of active AChE. Upregulation of AChE expression can be triggered by some peptides. Sources of exogenous AChE can be whole blood or purified AChE, either from human or nonhuman species.

Acetylcholinesterase inhibitors neostigmine and physostigmine inhibit induction of alpha-amylase activity during seed germination in barley, Hordeum vulgare var. Jyoti

Acetylcholine (ACh) is an important neurotransmitter whose non-neuronal biological roles are being widely accepted. ACh and components of its metabolism are present in plants. ACh and some inhibitors of acetylcholinesterase (AChE) share structural similarity (quaternary ammonium group) with some inhibitors of biosynthesis of a plant hormone, gibberellic acid (GA); e.g., 2-Isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride (AMO-1618) inhibits GA biosynthesis as well as AChE. The present study explores the possibility that ACh and antiAChE may inhibit GA biosynthesis. Seeds of barley var. Jyoti were germinated in the presence of ACh, its breakdown products - choline and acetate, and two antiAChE - neostigmine and physostigmine (all 10(-5) M). Alpha amylase activity in germinating seeds was measured as a reliable indicator of the level of GA biosynthesis. Alpha amylase activity in barley seeds was significantly reduced after 72 h of treatment with antiChE but not by ACh or its breakdown products. Since germinating barley seeds contain AChE, much of the ACh may have been broken down before its uptake. Quaternary ammonium antiChE neostigmine was more effective (50% inhibition at 10(-5) M) as compared to tertiary ammonium physostigmine (15% inhibition at 10(-5) M). ACh, choline, acetate, neostigmine and physostigmine (all 10(-5) M) did not affect formation of starch-iodine complex or activity of alpha-amylase per se. Our results indicate that quaternary ammonium inhibitors of AChE may inhibit GA biosynthesis.

Properties of Kaurene Synthetase from Marah macrocarpus

The kaurene synthetase from immature seeds of Marah macrocarpus (Greene) Greene was partially purified from cell-free homogenates of endosperm by a combination of QAE-Sephadex A-25 chromatography and hydroxyapatite chromatography and freed of contaminating phosphatase activity. The two catalytic activities associated with kaurene synthetase, the cyclization of geranylgeranyl-pyrophosphate to copalyl-pyrophosphate (activity A) and the cyclization of copalyl-pyrophosphate to ent-kaurene (activity B), were not even partially resolved from one another during these procedures. Both activities had identical elution profiles from a calibrated Sepharose 4B column corresponding to a molecular weight less than that of ovalbumin (45,000).The A and B activities had pH optima of 7.3 and 6.9, respectively. Both activities required millimolar concentrations of the following divalent cations in the order: Mg(2+) > Mn(2+) > Co(2+). Activities A and B were both sensitive to inhibition by Hg(2+), Cu(2+), p-hydroxymercuribenzoate, and N-ethylmaleimide, but activity B was much more sensitive than activity A. The average value of Km' (apparent Km in the absence of substrate inhibition) for geranylgeranyl-pyrophosphate was 1.6 mum. Values of 0.5 and 0.6 mum were obtained for Km' and Km, respectively, for copalyl-pyrophosphate. The Vm' values for the two activities were similar: 12 and 9 pmol/minute.mug protein for activities A and B, respectively.N,N-Dimethylaminoethyl-2,2-diphenylpentanoate (SKF-525A) and N,N-dimethylaminoethyl-2,2-diphenylphentyl ether (SKF-3301A), tributyl-2,4-dichlorobenzylphosphonium chloride (Phosfon D), tributyl-2,4-dichlorobenzylammonium chloride (Phosfon S), 2'-isopropyl-4'-(trimethylammonium chloride)-5'-methylphenyl piperidine-1-carboxylate (Amo-1618), 2-(N,N-dimethyl-N-heptylammonium bromide)-p-methan-1-ol (Q-58), and 2-(N,N-dimethyl-N-octylammonium bromide)-p-methan-1-ol (Q-64), at concentrations from 1 to 5 mum, were effective inhibitors of kaurene synthetase activity A. Acetylcholine chloride and 2-chloroethyl-trimethylammonium chloride were effective inhibitors of activity A only at concentrations of 5 mm or greater. Abscisic acid, indole-3-acetate, gibberellin A(1), gibberellin A(3), a mixture of gibberellins A(4) and A(7), gibberellin A(13), and N,N-dimethylaminosuccinamic acid (B995) were not inhibitory at any of the levels tested. None of these compounds was an effective inhibitor of activity B at concentrations less than 0.5 mm.

Cholinesterases from plant tissues. VI. Preliminary characterization of enzymes from Solanum melongena L. and Zea mays L

Enzymes capable of hydrolyzing esters of thiocholine have been assayed in extracts of Solanum melongena L. (eggplant) and Zea Mays L. (corn). The enzymes from both species are inhibited by the anti-cholinesterases neostigmine, physostigmine, and 284c51 and by AMO-1618, a plant growth retardant and they both have pH optima near pH 8.0. The enzyme from eggplant is maximally active at a substrate concentration of 0.15 mM acetylthiocholine and is inhibited at higher substrate concentrations. On the basis of this last property, the magnitude of inhibition by the various inhibitors, and the substrate specificity, we conclude that the enzyme from eggplant, but not that from corn, is a cholinesterase.

Cholinesterases from plant tissue: v. Cholinesterase is not pectin esterase

Several properties of the cholinesterase from Phaseolus aureus Roxb. and of pectin (methyl) esterases from both Phaseolus aureus and Lycopersicon esculentum (L.) Mill. are contrasted. Cholinesterase activity is inhibited by all of the concentrations of NaCl tested, from 0.05 m to 0.9 m, a property which differs sharply from published data pertaining to pectin esterase. Although crude preparations of cholinesterase contain pectin esterase activity, further purification by gel filtration of the cholinesterase results in a nearly complete elimination of the pectin esterase activity. The activity of neither the pectin esterase from Lycopersicon esculentum nor that from Phaseolus aureus is affected by 25 mum neostigmine, a potent inhibitor of the cholinesterase activity extracted from Phaseolus aureus.