Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Saturated and monounsaturated fatty acids are mainly synthetized in the brain, but some of them could originate from the diet; in contrast polyunsaturated fatty acids are derived from dietary linoleic and linolenic acid. Saturated fatty acid biosynthesis occurs via three main pathways in mammalian cells. One is de novo synthesis of fatty acids from acetyl-CoA via malonyl-CoA; this system has been isolated in soluble form (the soluble system) from various animal tissues including brain. The second and third pathways involve elongation: in the mitochondrial system, acetyl CoA is the principal substrate in extracts from all organs, even brain; in the microsomal system, however, malonyl-CoA acts as donor of the 2 carbon fragments. In vivo studies in brain have shown that very long chain fatty acids are synthesized by elongation rather than by a than by a de novo mechanism. Feeding animals with oils that have a low n-3 acid content (linolenic series) results in all brain cells and organelles reduced amounts of 22:6 n-3 which is compensated for by an increase in 22:5 n-6. The speed of recuperation from these anomalies is extremely slow for brain cells, organelles and microvessels, in contrast with other organs. Essential fatty acids for the brain could be those with very long chains as shown with cell culture. They are probably synthesized in the liver from linolenic acid. They can also be supplied directly by food. During the period of cerebral development there is a linear relation between the n-3 acid content of the brain and that of food until linolenic acid represents approx. 200 mg per 100 g of food (for 1200 mg linoleic acid). A decrease in acids of the linolenic series in the membranes results in a 40% reduction of Na-K-ATPase in nerve terminals and a 20% reduction in 5'-nucleotidase in whole brain homogenate. A diet low in linolenic acid leads to anomalies in the electroretinogram which disappear partially with age, it seriously affects learning tasks. The presence of linolenic acid in the diet confers a greater resistance to certain neurotoxic agents.
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PMID:Control of brain fatty acids. 207 91

Neuronal death generally involves, directly or indirectly, free radical attack and peroxidation. Targets are nucleic acids, proteins, the cytoskeleton, the extracellular matrix and especially membrane polyunsaturated fatty acids. a) One example for the fundamental role of fatty acids. Dietary fatty acids, and more particularly essential polyunsaturated fatty acids, have a direct influence on the composition of cerebral membranes, and hence on their functioning. Each of the two series of polyunsaturated fatty acids plays a particular role. In animals, a deficiency in linolenic acid causes serious perturbations in the nervous system. In fact, feeding animals with oils that have a low n-3 content leads to severe abnormalities in the composition of membranes, both of the brain and other organs. The rate of recovery from these anomalies is extremely slow in the brain, but rapid in the liver. Compared to certain other organs, the nervous system is neither protected against deficiency nor has it priority in the satisfaction if its needs. A decrease in acids of the linolenic series in the membranes results in a 40% reduction of Na-K-ATPase in nerve endings and a 20% reduction in 5'-nucleotidase. It also leads to anomalies in the electroretinogram which disappear with age. This deficiency in linolenic acid has little effect on motor function and disturbes activity and emotivity only slightly, but it seriously affects learning tasks. The presence of linolenic acid in the diet confers greater resistance to certain neurotoxic substances (triethyl lead, for example). Fatty acids essential for the brain could be those with very long chains. They are probably synthesized in the liver from linolenic and linoleic acids. They can also be supplied directly by food. However, if the diet contains a large proportion of very long chain fatty acids (fish oils), the lipid composition of all organs, including the brain, is altered. During the period of brain development there is a linear relation between the polyunsaturated fatty acid content of the brain and that of the diet. The requirement in linolenic acid is 200 mg/100 g of diet (0.4% of calories). That of linoleic acid is 1,200 mg/100 g of diet (2.4% of calories). b) Peroxidation of polyunsaturated fatty acids. Arachidonic acid is released by lysis of phospholipids (it is directly toxic), its peroxidized derivatives are extremely toxic. Peroxidation of membrane lipids alters enzymatic activity, the relationship between receptor and ligand, transport, and the symmetry of the lipid bilayer.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Free radicals, polyunsaturated fatty acids, cell death, brain aging]. 284 29

Subcellular fractions of nuclei, mitochondria, endoplasmic reticulum, plasma membrane and cytosol were prepared from liver and hepatoma 7288CTC. Marker enzyme activities, biochemical compositions and electron microscopy were used to establish purity. Hepatoma NADH: cytochrome C reductase and 5'-nucleotidase exhibited abnormal subcellular distributions. The lipids from the subcellular fractions were examined in detail. Mitochondria and plasma membranes were characterized by elevated percentages of diphosphatidylglycerol and sphingomyelin, respectively, in both tissues. All hepatoma subcellular fractions contained dramatically elevated levels of sphingomyelin and cholesterol, two components that form preferential strong complexes in vitro. The fatty acid composition of hepatoma sphingomyelin differed markedly from liver and, unlike liver, did not exhibit organelle specific compositions. Some hepatoma lipid classes contained reduced percentages of palmitate while others contained higher levels. Hepatoma phosphatidylcholine and phosphatidylethanolamine from organelles contained lower percentages of long chain polyunsaturated fatty acids than liver. Generally, unique fatty acid profiles exhibited by individual phospholipid classes of liver subcellular fractions were absent or much reduced in the hepatoma. The ratios of oleate to vaccenate were near one for most of the phospholipid classes of most liver fractions, but all hepatoma classes, with few exceptions, contained a much higher percentage of oleate in all subcellular fractions. The hypothesis is proposed that the origin of some acyl moieties for the biosynthesis of various hepatoma lipid classes differs from liver sources. The possible changes in acyl pools, sources and compartments for complex lipid biosynthesis could result in change in the quantities of molecular species that could contribute to the abnormal properties of the hepatoma membranes.
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PMID:A comparison of lipids from liver and hepatoma subcellular membranes. 371 48

The content and composition of neutral lipids and phosphoglycerides from full-grown prophase-arrested Bufo arenarum Hensel oocytes and from their ghost preparations were studied. The ghosts obtained are highly enriched in plasma membrane as suggested by the activity of 5'-nucleotidase, a marker enzyme, and the level of typical membrane components such as sphingomyelin, phosphatidylserine (PS), phosphatidylinositol (PI), and phosphatidic acid. In whole oocytes, triacylglyceride (TAG) comprises about 60% of the total lipids followed by phosphatidylcholine (PC), cholesterol, and phosphatidylethanolamine (PE). TAG and diacylglycerides have a similar unsaturation index. PC and PE account for about 80% of the phosphoglycerides in the whole oocyte and in their plasma membrane-enriched fractions. Arachidonic acid (20:4n-6), 18:0, and 16:0 make up about 80 mol% of the total fatty acids in PI in whole oocytes and ghost fractions. The unsaturation index in PS is higher in intact oocytes than in ghost preparations, probably owing to the significant amount of 20:4n-6 which comprises 23 mol% of the total fatty acids in whole oocytes. The fatty acid profile in phosphatidic acid from whole oocytes is rather different from that in ghosts. Sphingomyelin contains mainly saturated and monounsaturated fatty acids, 24:1 being the principal very long chain unsaturated fatty acid in both oocytes and ghosts.
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PMID:Lipidic characterization of full-grown amphibian oocytes and their plasma membrane-enriched fractions. 878 47