Choline oxidation

Weigel, P., Lerma, C. Hanson, A.D. (1988). Choline oxidation by intact spinach chloroplasts. Plant Physiology, 86, 54-60. 

It was shown by Strength et al. (261) that the oxidation of choline by a particulate preparation from rat liver was considerably enhanced upon addition of NAD. Others showed that choline oxidation by isolated rat liver mitochondria was completely inhibited by Amytal when oxygen, cytochrome c, ferricyanide, or methylene blue was the electron acceptor -264) Choline dehydrogenase activity of particles and soluble prepa-... 

It has been shown that the oxidation of choline by isolated rat liver mitochondria is biphasic (269). The initial phase of choline oxidation is slow and coupled to the uptake of inorganic phosphate. The ensuing phase is 3-5 times faster and not coupled to phosphorylation. The slow phase can be extended in the presence of Mg-+ and ADP or ATP. These compounds are considered to control the permeability of mitochondria to choline (270). Calcium ions and conditions which result in mitochondrial swelling and membrane disruption have been shown to increase choline oxidation (266, 271). 

NADH dehydrogenase and, 189 ubiquinone reductase and, 178,182,183 Cholesterol, side chain cleavage, 83, 84-85 Choline, oxidation to betaine, 260 Choline dehydrogenase electron transport system and, 261-263 properties, 260-201 Chromatium sulfate reduction by, 281 transhydrogenase of, 54 function of, 80 molecular properties, 58, 69 purification, 55, 56 Chromium... 

One-carfaon cycle a cycle of methyl transfer and methyl oxidation involving glycine, sarcosine, dimethylglycine, betaine and choline, first proposed in 1958 from observations on the oxidation of dimethylglycine and sarcosine by rat liver mitochondria [Mackenzie Frisell, J. Biol. Chem. 232 (1958) 417-427]. The existence of a 0-c.c. is now confirmed it involves choline oxidation in mitochondria and phosphatidylcholine synthesis in the endoplasmic reticulum (Fig.). [A.J. Wittwer C.Wagner J. Biol. Chem. 256 (1981) 4102- 108, 4109-4115]... 

The choline electrode usually consists of an amperometric transducer and immobilized choline oxidase. The most frequently used electrochemical transducers are hydrogen peroxide electrodes (26-28,33-36). The amperometric signal in this case is due to electrooxidation of hydrogen peroxide, which is the co-product of the enzymatic choline oxidation (equation 2). Oxygen amperometric sensors (Qark-type electrodes) have been also used as basic transducers for choline electrode construction (29, 32, 37). The signal in this case is based on the reduction of molecular oxygen which is the co-reactant in reaction (equation 2). Redox mediators hexacyanoferrate (26), ferrocene derivatives (38) and tetracyanoquinodimethane (39) have also been used in the construction of choline electrodes. 

A potentiometric electrode based on direct mediatorless bio-electrocatalysis for determination of choline and butyryl-choline is developed. The electrode consists of a carbon based material and enzymes peroxidase and choline oxidase co-immobilized on the electrode surface. Choline oxidase catalyzes the reaction of choline oxidation accompanied with hydrogen peroxide formation. Hydrogen peroxide acts as a substrate of the enzyme peroxidase. 

Trimethylamine, CjH N, (CH3J3N. Colourless liquid with a strong fishy odour, miscible with water, m.p. — I24 C, b.p. 3-5°C. It occurs naturally in plants, herring brine, bone oil and urine. It reacts with hydrogen peroxide to give trimethylamine oxide and with ethylene oxide to give choline its commercial importance stems chiefly from this latter reaction. 

An earlier procedure for the production of choline and its salts from natural sources, such as the hydrolysis of lecithin (23), has no present-day apphcation. Choline is made from the reaction of trimethyl amine with ethylene oxide [75-21-8] or ethylene chlorohydrin [107-07-5J. 

The chlorohydrin process (24) has been used for the preparation of acetyl-P-alkylcholine chloride (25). The preparation of salts may be carried out mote economically by the neutralization of choline produced by the chlorohydrin synthesis. A modification produces choline carbonate as an intermediate that is converted to the desired salt (26). The most practical production procedure is that in which 300 parts of a 20% solution of trimethyl amine is neutralized with 100 parts of concentrated hydrochloric acid, and the solution is treated for 3 h with 50 parts of ethylene oxide under pressure at 60°C (27). 

Triethylenemelamine Ethylene oxide Chlorambucil Choline dihydrogen citrate Etofibrate Melphalan Nimorazole Nonoxynol Tyloxapol Uracil mustard... 

Choline, a component of the phospholipids in cell membranes, can be prepared by Sn2 reaction of trimethylamine with ethylene oxide. Show the structure of choline, and propose a mechanism for the reaction. 

DMN oxidative demethylation has been shown to be a liver mi-crosome cytochrome P-450 monooxygenase (10) Lotlikar et al. (11) found that a reconstituted enzyme system, consisting of cytochrome P-450, NADPH-cytochrome P-450 reductase and phosphatidyl choline was effective in catalyzing the demethylation of DMN. The most commonly accepted mechanism for the oxidative demethylation of DMN and, by extension, of other dialkyInltrosamlnes is shown in Scheme 1. 

Hepatic steatosis usually is a result of excessive administration of carbohydrates and/or lipids, but deficiencies of carnitine, choline, and essential fatty acids also may contribute. Hepatic steatosis can be minimized or reversed by avoiding overfeeding, especially from dextrose and lipids.35,38 Carnitine is an important amine that transports long-chain triglycerides into the mitochondria for oxidation, but carnitine deficiency in adults is extremely rare and is mostly a problem in premature infants and patients receiving chronic dialysis. Choline is an essential amine required for synthesis of cell membrane components such as phospholipids. Although a true choline deficiency is rare, preliminary studies of choline supplementation to adult patients PN caused reversal of steatosis. 

Acetylcholine + H20 AChE > Thiocholine + Acetic acid 2 Thiocholine Oxidation v Dithio-bis-choline+2H++ 2e"... 

On the other hand, several oxidases are known to generate hydrogen peroxide, acting as an oxidant in the CL system, from corresponding substrates. IMERs in which the oxidases are immobilized on adequate supporting materials such as glass beads have been developed. IMERs are often used for flow injection with CL detection of uric acid and glucose, and are also applicable to the CL determination of acetylcholine, choline, polyamines, enzyme substrates, etc., after online HPLC separation. 

In this system, choline formed by acetylcholinesterase is oxidized by choline oxidase and the hydrogen peroxide produced is determined using the luminol/peroxidase CL reaction. The sensor has been used for the analysis of Paraoxon and Aldicarb pesticides, with detection limits of 0.75 pg/L and 4 pg/ L, respectively. Recoveries in the range of 81-108% in contaminated samples of soils and vegetables were obtained. 

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