Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.1.2.13 (aldolase)
3,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activities of enzymes involved in fructose metabolism were measured in samples of human kidney cortex and medulla. The enzymes are ketohexokinase, aldolase, NAD- and NADP-dependent alcohol dehydrogenase, aldehyde dehydrogenase, triokinase and glycerate kinase; hexose biphosphatase and sorbitol dehydrogenase were also investigated. With the exception of glycerate kinase, all enzymes involved in fructose metabolism were found in the human cortex and medulla. The enzyme levels in the medulla were low in comparison with the cortex.
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PMID:Enzymes of fructose metabolism in human kidney. 16 31

In this research on metabolic effects of a high fructose diet, we studied the duration of these effects by measuring the specific activity of 8 enzymes stimulated by such a diet, on days, 0, 3, 6, 9, 15, after the return to a normal diet. In the intestinal mucosa, ketohexokinase, aldolase, triokinase, fructose-diphosphatase, and glucose-6-phosphatase specific activities were still entirely or partially stimulated on the 15th day after return to the standard diet. The stimulation of glucose-6-phosphatase and pyruvate kinase specific activities stopped quickly. In the liver, with the exception of fructose-diphosphatase, the return to basic values was much quicker than in intestine. In 7 enzymes out of 8 it was realized in 9 days or less. When a high fructose diet gives way to a normal one, return to basic values comes so much the quicker as activation has needed longer to appear.
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PMID:Dietary regulation of fructose metabolism in the intestine and in the liver of the rat. Duration of the effects of a high fructose diet after the return to the standard diet. 172 50

Ketohexokinase (EC 2.7.1.3) was purified to homogeneity from human liver, and fructose-bisphosphate aldolase (EC 4.1.2.13) was partially purified from the same source. Ketohexokinase was shown, by column chromatography and polyacrylamide-gel electrophoresis, to be a dimer of Mr 75000. Inhibition studies with p-chloromercuribenzoate and N-ethylmaleimide indicate that ketohexokinase contains thiol groups, which are required for full activity. With D-xylulose as substrate, ketohexokinase and aldolase can catalyse a reaction sequence which forms glycolaldehyde, a known precursor of oxalate. The distribution of both enzymes in human tissues indicates that this reaction sequence occurs mainly in the liver, to a lesser extent in the kidney, and very little in heart, brain and muscle. The kinetic properties of ketohexokinase show that this enzyme can phosphorylate D-xylulose as readily as D-fructose, except that higher concentrations of D-xylulose are required. The kinetic properties of aldolase show that the enzyme has a higher affinity for D-xylulose 1-phosphate than for D-fructose 1-phosphate. These findings support a role for ketohexokinase and aldolase in the formation of glycolaldehyde. The effect of various metabolites on the activity of the two enzymes was tested to determine the conditions that favour the formation of glycolaldehyde from xylitol. The results indicate that few of these metabolites affect the activity of ketohexokinase, but that aldolase can be inhibited by several phosphorylated compounds. This work suggests that, although the formation of oxalate from xylitol is normally a minor pathway, under certain conditions of increased xylitol metabolism oxalate production can become significant and may result in oxalosis.
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PMID:The purification and properties of human liver ketohexokinase. A role for ketohexokinase and fructose-bisphosphate aldolase in the metabolic production of oxalate from xylitol. 299 95

The longitudinal localization of nine enzymes of the carbohydrate metabolism was studied in rats fed standard or high fructose diets, two months after a reciprocal jejuno-ileal transposition. In the ileal segment transposed to jejunal location, an adaptive increase of mucosal mass was observed, but the functional characteristics of enterocytes remained the same in the case of triokinase, aldolase, triose phosphate isomerase, glucose-6-phosphate isomerase and glucose-6-phosphatase activities. In the case of ketohexokinase and hexokinase activities, the functional properties of cells tended to resemble that of jejunum, as revealed by a significant increase in the specific enzyme activity. In the jejunum transposed to the place of the ileum, the fundamental properties of enterocytes and the functional capacity of the gut were maintained except in the case of fructose-1.6-bis phosphatase and of glucose-6-phosphatase. The high fructose diet did not facilitate the re-establishment of the gradient in its normal, aboral, direction. Indeed except for glucose-6-phosphatase, the enzymes of the jejunum transposed to the place of the ileum kept a high sensitivity and the enzymes of transposed ileum a low sensitivity to dietary fructose. Our conclusion is that the response to the diet depends more on the original position of the intestinal segment than on the local nutritional conditions and therefore that the basal activity of the majority of the intracellular enzymes implicated in carbohydrate metabolism and also their regulatory systems, are an intrinsic characteristic of the intestinal cells.
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PMID:[Intestinal adaptation and enzymatic changes following reciprocal jejunoileal transposition in rats. Effects of a high-fructose diet]. 397 35

The enzyme activities involved in fructose metabolism were measured in samples of human liver. On the basis of U/g of wet-weight the following results were found: ketohexokinase, 1.23; aldolase (substrate, fructose-1-phosphate), 2.08; aldolase (substrate, fructose-1,6-diphosphate), 3.46; triokinase, 2.07; aldehyde dehydrogenase (substrate, D-glyceraldehyde), 1.04; D-glycerate kinase, 0.13; alcohol dehydrogenase (nicotinamide adenine dinucleotide [NAD]) substrate, D-glyceraldehyde), 3.1; alcohol dehydrogenase (nicotinamide adenine dinucleotide phosphate [NADP]) (substrate, D-glyceraldehyde), 3.6; and glycerol kinase, 0.62. Sorbitol dehydrogenases (25.0 U/g), hexosediphosphatase (4.06 U/g), hexokinase (0.23 U/g), and glucokinase (0.08 U/g) were also measured. Comparing these results with those of the rat liver it becomes clear that the activities of alcohol dehydrogenases (NAD and NADP) in rat liver are higher than those in human liver, and that the values of ketohexokinase, sorbitol dehydrogenases, and hexosediphosphatase in human liver are lower than those values found in rat liver. Human liver contains only traces of glycerate kinase. The rate of fructose uptake from the blood, as described by other investigators, can be based on the activity of ketohexokinase reported in the present paper. In human liver, ketohexokinase is present in a four-fold activity of glucokinase and hexokinase. This result may explain the well-known fact that fructose is metabolized faster than glucose.
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PMID:Enzymes of fructose metabolism in human liver. 438 49

The adaptative response of a diet containing 60% fructose on the activity of those enzymes which are involved in the metabolism of fructose was measured in the liver and in the jejunal mucosa of rats over a period of 12 days. Control animals received isocaloric amounts of glucose or starch. Under fructose feeding there was a marked increase in the activity of fructose-1-phosphate aldolase (3-fold), ketohexokinase (2--3-fold), and triokinase (3-fold) in the jejunal mucosa. In the liver, however, a significant increase in enzyme activity could only be seen for triokinase (2--3-fold), whereas the activity of the other enzymes measured were only slightly or not at all altered. The activity of the three enzymes mentioned above were elevated to a maximum within 3 days after feeding the fructose diet. In the following time of observation no major further changes occurred. The results show that fructose feeding in comparison to a glucose or starch containing diet leads to a marked adaptative increase in the activity of those enzymes, which are involved in the breakdown of fructose, only in the jejunal mucosa.
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PMID:Adaptative changes of activity of enzymes involved in fructose metabolism in the liver and jejunal mucosa of rats following fructose feeding. 625 5

By introducing fructose into the glycolysis, it is possible to stimulate ATP formation. As is the case in animal experiments, in human lenses, too, the first step in the phosphorylation to fructose-1-phosphate via the enzyme ketohexokinase. The present investigation deals with the question whether enzymes present in the lens are responsible for the further steps in fructose degradation. Particularly the aldolase isoenzyme C splits fructose-1-phosphate into glyceraldehyde and dihydroxyacetone phosphate in the same way as in glucose catabolism. Dihydroxyacetone phosphate can further be directly degraded and thus utilized to ATP formation. From glyceraldehyde, glycerol (aldose reductase) or glycerate (aldehyde dehydrogenase) can be formed. The presence of triosekinase, which phosphorylates glyceraldehyde directly to glyceraldehyde-3-phosphate, could only be determined in the lens tissue of young animals. The presence of glycerokinase (glycerol leads to glycerophosphate) could not be verified. Thus, in the lens tissue 1 ATP molecule net per fructose molecule can be formed. In older age, the glucose breakdown is limited by hexokinase and phosphofructokinase, so that the glucose, after transformation via the sorbitol pathway to fructose, can also be utilized for the energy metabolism.
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PMID:Investigations of the enzymes involved in the fructose breakdown in the cattle lens. 628 47

Male, Sprague-Dawley rats were weaned prematurely (postnatal day 17) to a starch-based diet. At the age of 182 days, half of the rats were fed for 14 days a diet in which sucrose supplied 40% of the energy. Early weaning led to increases in the activities of hepatic glucose-6-phosphate dehydrogenase (G6PD) and malic enzyme (ME). Compared with spontaneously weaned rats, prematurely weaned animals also showed increases in hepatic lipogenesis in vivo and in liver cholesterol levels. However, early weaning did not influence intraperitoneal glucose tolerance, plasma cholesterol concentrations or the activities of hepatic ketohexokinase (KHK), fructose-1-phosphate aldolase (FIPA) and triokinase (TK). Sucrose feeding led to deterioration of glucose tolerance and to enhanced hepatic lipogenesis in vivo. Sucrose-fed rats also showed increases in the total activities of hepatic G6PD, ME, KHK, FIPA and TK. There was a positive interaction in effects on liver size between early weaning and dietary sucrose. In general, however, there were no differences between prematurely and normally weaned rats in their responses to sucrose. The results did not support the idea that dietary adaptations in early life alter the manner in which adult rats respond to dietary stimuli.
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PMID:Effects of premature weaning on the metabolic response to dietary sucrose in adult rats. 707 28

Male, Sprague-Dawley rats were weaned prematurely (post-natal day 17) to a starch-based diet. Compared with normally-weaned rats, prematurely-weaned animals showed increases in the activities of hepatic glucose-6-phosphate dehydrogenase (G6PD) and malic enzyme (ME), and a fall in serum cholesterol level within 1 day. These enzymatic changes occurred sooner and were more pronounced when the diet of prematurely-weaned rats supplied 20% of the energy from sucrose, but the initial fall in serum cholesterol levels was smaller than in animals weaned prematurely to the control diet. Sucrose also led to an early rise in the activity of hepatic triokinase, but did not influence ketohexokinase or fructose-1-phosphate aldolase. Sucrose consumption resulted in an increase in lipogenesis in vivo in the liver and carcass and in serum cholesterol concentration on postnatal day 30, but animals weaned to the control diet were comparable with normally-weaned rats at the time. Early weaning led to elevation in the activities of hepatic G6PD and ME in 122-day-old rats, even though the control diet was fed from the age of 30 days. This response was not altered by the type of carbohydrate fed during the initial weaning period. Sucrose consumption during the weaning period did not exert long-term effects on the activities of hepatic fructolytic enzymes or in serum cholesterol levels.
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PMID:Immediate and late effects of premature weaning of rats to diets containing starch or low levels of sucrose. 728 3

The effects of vanadate, an oxidized form of vanadium, on glucose metabolism of the lens in diabetic rats were studied. Five-week-old male Sprague-Dawley rats were rendered diabetic with intraperitoneal injection of streptozotocin (50 mg/kg). One week later, the diabetic rats were given 0.2 g/l NaVO3 -5g/l NaCl solution in drinking water ad libitum for 2 weeks and biochemical parameters in their lenses were determined. Blood glucose levels significantly decreased in the vanadate-administered diabetic rats (DV group), compared with the diabetic rats given no vanadate (D group). In the DV group, a significant decrease was observed in lens fructose content compared with the D group. Lens ketohexokinase activity tended to be higher and lens aldolase activity was significantly higher in the DV group than in the D group. These results indicate that vanadate accelerates the metabolic reaction from sorbitol pathway to glycolysis.
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PMID:[Effects of vanadate on glucose metabolism in the lens of rats with streptozotocin-induced diabetes--ketohexokinase and aldolase activity]. 788 27


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