A quinoprotein. In many bacteria, plants and animals, the osmoprotectant betaine is synthesized using different enzymes to catalyse the conversion of (1) choline into betaine aldehyde and (2) betaine aldehyde into betaine. In plants, the first reaction is catalysed by EC 1.14.15.7, choline monooxygenase, whereas in animals and many bacteria, it is catalysed by either membrane-bound choline dehydrogenase (EC 1.1.99.1) or soluble choline oxidase (EC 1.1.3.17) . The enzyme involved in the second step, EC 1.2.1.8, betaine-aldehyde dehydrogenase, appears to be the same in plants, animals and bacteria.
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SYSTEMATIC NAME
IUBMB Comments
choline:acceptor 1-oxidoreductase
A quinoprotein. In many bacteria, plants and animals, the osmoprotectant betaine is synthesized using different enzymes to catalyse the conversion of (1) choline into betaine aldehyde and (2) betaine aldehyde into betaine. In plants, the first reaction is catalysed by EC 1.14.15.7, choline monooxygenase, whereas in animals and many bacteria, it is catalysed by either membrane-bound choline dehydrogenase (EC 1.1.99.1) or soluble choline oxidase (EC 1.1.3.17) [4]. The enzyme involved in the second step, EC 1.2.1.8, betaine-aldehyde dehydrogenase, appears to be the same in plants, animals and bacteria.
oxygen is not the preferred electron acceptor even though the enzyme is able to utilize it. Phenazine methosulfate can act as artificial cofactor. Cytochrome c and ferricyanide give poor activity
the enzyme belongs to the glucose-methanol-choline (GMC) enzyme oxidoreductase enzyme superfamily, members of the family contain a glycine box. Other members of the family all use FAD as cofactor, overall structures and active sites of members of the GMC oxidoreductase enzyme superfamily, overview
the enzyme is associated with male infertility. Absence of CHD enzyme activity causes diminished sperm motility, and mitochondrial alterations are described in testis as well as liver, kidney and heart. Impairments in human CHD activity are associated with homocysteinuria, an accumulation of homocysteine that represents an independent risk factor for cardiovascular diseases. It exists a correlation between high concentrations of choline, low concentrations of glycine betaine in blood and a high-risk profile for cardiovascular disease. Choline deficiency the brain may degrade the membrane phospholipids of the neurons in order to recycle choline for the production of acetylcholine. Choline is involved in the global hypomethylation of hepatic DNA of rats fed a low choline diet, different rate of development of the hippocampus in the fetal brains of rodent models in the case of low and high maternal choline intake. The folate content in the liver of choline deficient rats decreases by 31% compared to control rats
the enzyme oxidizes choline. The regulation of the concentration of choline in tissues and blood is very important as choline plays key roles in different pathways. Choline is involved in the epigenetic regulation of gene expression through DNA methylation, in the biosynthesis of lipoproteins and membrane phospholipids and in the biosynthesis of the neurotransmitter acetylcholine. It is therefore important for the integrity of cell membranes, lipid metabolism and nerve function. Choline is considered an important nutrient for fetal and brain development, and choline is a constituent of phospholipids involved in signal transduction, such as phosphatidylcholine and plasmalogen, and of the phospholipid platelet activating factor. The metabolism of choline is also interrelated with the metabolism of folate. CHD is important for the catabolic utilization of choline when the latter is administered as a pharmacological agent, because choline is involved in the stimulation of cholinergic neuronal activity and in restoring phosphatidylcholine levels in the neuronal membrane, thus displaying a neuroprotective action relevant for diseases such as memory and cognitive deficits. CHD, predominantly active in the two main detoxifying organs liver and kidney, determines the half-life of choline in blood. The metabolic oxidation of choline is related to the risk of developing breast cancer
rapid turnover of choline when administered as a drug, about 50% of injected choline are directly eliminated via liver and kidney. Structure homology modeling
CHD contains an N-terminal cleavable mitochondrial targeting presequence of 34 amino acids and two cleavage sites may be present for recognition and processing by mitochondrial processing protease and inner membrane protease, mature CHD begins with amino acid 35
using column chromatography of the chemically modified enzyme with 5,5'-dithiobis(2-nitrobenzoic acid) on DEAE-Sepharose CL-6B and choline-Sepharose 4B with C3-spacer, subsequent release of the thionitrobenzoate with dithiothreitol, and a second column chromatography on DEAE-Sepharose CL-6B in the presence of 0.1% Triton X-100
study of prognostic biomarkers for breast cancer identifies the expression of CHD among three human genes controlled by estrogens, and shows that this is a strong predictor of the outcome of treatment with tamoxifen in early-stage (ER)-positive breast cancer patients
Liver choline dehydrogenase and kidney betaine-homocysteine methyltransferase expression are not affected by methionine or choline intake in growing rats