Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Interstrain differences in red blood cell enzyme activities were studied in mice (BALB/c, C57BL/6, C3H/He, DBA/2 and ddY) and rats (Donryu, F344/N, SD, Wistar and Wistar/ST), and were also compared with hamster, guinea-pig and rabbit. 2. The enzyme activities measured were: glutathione S-transferase (GST), glucose-6-phosphate dehydrogenase (G-6-PD), 6-phosphogluconate dehydrogenase (6-PGD), NADPH-diaphorase (ND), hexokinase (Hx), glutamate oxaloacetate transaminase (GOT), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE). 3. There were marked variations in the activities of some red cell enzymes (e.g. GST, Hx, ND), while others (e.g. G-6-PD, 6-PGD) were much less variable both within different strains and species.
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PMID:Interstrain differences in red cell enzyme activities in mice and rats. 178 55

The early stages of insulin-dependent diabetes mellitus are characterized by a selective inability to secrete insulin in response to glucose, coupled to a better response to nonnutrient secretagogues. The deficient glucose response may be a result of the autoimmune process directed toward the beta-cells. Interleukin-1 (IL-1) has been suggested to be one possible mediator of immunological damage of the beta-cells. In the present study we characterized the sensitivity of beta-cells to different secretagogues after human recombinant IL-1 beta (rIL-1 beta) exposure. Furthermore, experiments were performed to clarify the biochemical mechanisms behind the defective insulin response observed in these islets. Rat pancreatic islets were isolated and kept in tissue culture (medium RPMI-1640 plus 10% calf serum) for 5 days. The islets were subsequently exposed to 60 pM human recombinant IL-1 beta during 48 h in the same culture conditions as above and examined immediately after IL-1 exposure. The rIL-1 beta-treated islets showed a marked reduction of glucose-stimulated insulin release. Stimulation with arginine plus different glucose concentrations, and leucine plus glutamine partially counteracted the rIL-1 beta-induced reduction of insulin release. The activities of the glycolytic enzymes hexokinase, glucokinase, and glyceraldehyde 3-phosphate dehydrogenase, were similar in control and IL-1-exposed islets. Treatment with IL-1 also did not impair the activities of NADH+- and NADPH+-dependent glutamate dehydrogenase, glutamate-aspartate transaminase, glutamate-alanine transaminase, citrate synthase, and NAD+-linked isocitrate dehydrogenase. The oxidation of D-[6-14C]glucose and L-[U-14C]leucine were decreased by 50% in IL-1-treated islets. Furthermore, there was a significant decrease in the ratios of [2-14C]pyruvate oxidation/[1-14C]pyruvate decarboxylation and L-[U-14C]leucine oxidation/L-[1-14C]leucine decarboxylation, indicating that IL-1 decreases the proportion of generated acetyl-coenzyme-A residues undergoing oxidation. However, in the presence of IL-1 there was a significant increase in L-[U-14C]glutamate oxidation. These combined observations suggest that exposure to IL-1 induces a preferential decrease in glucose-mediated insulin release and mitochondrial glucose metabolism. This mitochondrial dysfunction seems to reflect an impairment in proximal steps of the Krebs cycle. It is conceivable that the IL-1-induced suppression and shift in islet metabolism can be an explanation for the beta-cell insensitivity to glucose observed in the early phases of human and experimental insulin-dependent diabetes mellitus.
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PMID:Differential sensitivity to beta-cell secretagogues in cultured rat pancreatic islets exposed to human interleukin-1 beta. 266 6

The effects of vitamin B6 on erythrocyte metabolism, erythrocyte hemoglobin O2 affinity (P50), and nonenzymatic glycosylation were studied in 15 Caucasian men with type II (non-insulin-dependent) diabetes mellitus. A control group of 13 healthy Caucasian men was also evaluated. Before treatment, diabetic subjects had low mean cell hemoglobin concentration values and increases in both erythrocyte 2,3-diphosphoglycerate (2,3-DPG) levels and erythrocyte hexokinase activities. Although all three of these changes are associated with a decrease in hemoglobin O2 (Hb-O2) affinity, P50 values were normal in diabetic subjects. Moreover, P50 values normalized to pH 7.4 (P50(7.4] were inversely related to the level of glycosylated hemoglobin (HbA1c). Both erythrocyte 2,3-DPG and erythrocyte ATP were also inversely related to HbA1c. Vitamin B6 nutriture, as determined by erythrocyte aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, was normal in all diabetic subjects before vitamin B6 therapy. Nonetheless, HbA1c levels decreased after 6 wk of treatment with 150 mg/day pyridoxine and increased again during placebo administration. These changes were not explained by changes in fasting blood glucose. Pyridoxine therapy also decreased P50(7.4) values and increased erythrocyte AST and ALT activities but had no effect on 2,3-DPG, ATP, or the activities of hexokinase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase. These observations suggest that 1) nonenzymatic glycosylation may play a role in regulating both erythrocyte metabolism and Hb-O2 affinity in diabetic subjects, and 2) vitamin B6 therapy may modify nonenzymatic glycosylation of hemoglobin in this population.
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PMID:Erythrocyte O2 transport and metabolism and effects of vitamin B6 therapy in type II diabetes mellitus. 273 64

Energy metabolism in proliferating cultured rat thymocytes was compared with that of freshly prepared non-proliferating resting cells. Cultured rat thymocytes enter a proliferative cycle after stimulation by concanavalin A and Lymphocult T (interleukin-2), with maximal rates of DNA synthesis at 60 h. Compared with incubated resting thymocytes, glucose metabolism by incubated proliferating thymocytes was 53-fold increased; 90% of the amount of glucose utilized was converted into lactate, whereas resting cells metabolized only 56% to lactate. However, the latter oxidized 27% of glucose to CO2, as opposed to 1.1% by the proliferating cells. Activities of hexokinase, 6-phosphofructokinase, pyruvate kinase and aldolase in proliferating thymocytes were increased 12-, 17-, 30- and 24-fold respectively, whereas the rate of pyruvate oxidation was enhanced only 3-fold. The relatively low capacity of pyruvate degradation in proliferating thymocytes might be the reason for almost complete conversion of glucose into lactate by these cells. Glutamine utilization by rat thymocytes was 8-fold increased during proliferation. The major end products of glutamine metabolism are glutamate, aspartate, CO2 and ammonia. A complete recovery of glutamine carbon and nitrogen in the products was obtained. The amount of glutamate formed by phosphate-dependent glutaminase which entered the citric acid cycle was enhanced 5-fold in the proliferating cells: 76% was converted into 2-oxoglutarate by aspartate aminotransferase, present in high activity, and the remaining 24% by glutamate dehydrogenase. With resting cells the same percentages were obtained (75 and 25). Maximal activities of glutaminase, glutamate dehydrogenase and aspartate aminotransferase were increased 3-, 12- and 6-fold respectively in proliferating cells; 32% of the glutamate metabolized in the citric acid cycle was recovered in CO2 and 61% in aspartate. In resting cells this proportion was 41% and 59% and in mitogen-stimulated cells 39% and 65% respectively. Addition of glucose (4 mM) or malate (2 mM) strongly decreased the rates of glutamine utilization and glutamate conversion into 2-oxoglutarate by proliferating thymocytes and also affected the pathways of further glutamate metabolism. Addition of 2 mM-pyruvate did not alter the rate of glutamine utilization by proliferating thymocytes, but decreased the rate of metabolism beyond the stage of glutamate significantly. Formation of acetyl-CoA in the presence of pyruvate might explain the relatively enhanced oxidation of glutamate to CO2 (56%) by proliferating thymocytes.
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PMID:Glutamine and glucose metabolism during thymocyte proliferation. Pathways of glutamine and glutamate metabolism. 286 9

A methodology is described for analyzing single human ova for 8 or 9 different metabolic enzymes, or 4 or 5 enzymes plus as many metabolites. This overcomes an obstacle to the study of human ovum metabolism: the severe limitation of usable material. Results obtained with this methodology, applied to discarded specimens from an in vitro fertilization program, indicate that in spite of imperfections these ova can provide a valid picture of the metabolic characteristics of normal human ova. Data are presented for 17 enzymes from 8 metabolic pathways in human and mouse ova. Relative to size, 10 of the enzymes were substantially higher in human than mouse ova. Most dramatically so were 2 enzymes of fatty acid metabolism (10-fold and 15-fold), hexokinase (9-fold), and aspartate aminotransferase (19-fold). This suggests that major species differences in metabolism are present. The validity of the human data, in spite of restriction to discarded material, is supported by (1) consistency of results among most of the ova, 2] concordance between average levels with those of rare specimens that were discarded because sperm were not available, and (3) the presence of adenosine triphosphate (ATP) concentrations similar to those of normal mouse ova. Surprisingly, both human and mouse ova contain phosphocreatine at levels nearly equal of those of ATP.
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PMID:Contrast in levels of metabolic enzymes in human and mouse ova. 290 84

We recently described a preferential reduction of the secretory response to nutrient secretagogues (glucose; leucine plus glutamine) in islets maintained in culture after in vitro exposure to streptozotocin (SZ). The present study is an attempt to further clarify the biochemical mechanisms behind this defective insulin response. Mouse pancreatic islets were collagenase isolated and, after 4-5 days in culture, exposed during 30 min at 37 C to 1.8 mM SZ or vehicle alone (controls). The islets were subsequently cultured for 7 days in medium RPMI 1640 plus 10% calf serum, before the enzymatic and metabolic studies were performed. The activities of the glycolytic enzymes, hexokinase, glucokinase, and glyceraldehyde 3-phosphate dehydrogenase, were similar in the control and SZ-exposed islets. The relative amount of cytosolic and mitochondria-bound hexokinase was also unaffected by SZ. However, there was a 30-40% decrease in the activity of NAD+- and NADP+-dependent glutamate dehydrogenase and glutamate-aspartate transaminase in the SZ-treated islets. This coincided with a 40% decrease in L-[U-14C]glutamine oxidation in the SZ-treated islets. The D-glucose catabolism was further examined in the presence of D-[5-3H] and D-[6-14C] glucose. There was no difference between control and SZ islets in terms of glucose utilization at either 1.7 or 16.7 mM glucose. The oxidation of D-[6-14C]glucose was nevertheless decreased by more than 50% in SZ islets incubated at 16.7 mM (but not 1.7 mM) glucose. Altogether, these converging observations suggest a perturbation of distal regulatory processes, apparently at the mitochondrial level, in the D-glucose and L-glutamine catabolism of SZ-exposed islets. Whether this reflects a primary action of SZ on the islet mitochondria, or an inhibitory effect of SZ on the synthesis of mitochondrial enzymes, as a result of nuclear DNA damage, remains to be elucidated.
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PMID:Defective catabolism of D-glucose and L-glutamine in mouse pancreatic islets maintained in culture after streptozotocin exposure. 296 23

The effect of hypoxia and post-hypoxic recovery were studied in gastrocnemius muscle of young-adult and mature beagle dogs. Furthermore, the possible interference of pharmacological treatment with nicergoline was evaluated in these conditions. Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose 6-phosphate, pyruvate, lactate), Kreb's cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate) and related free amino acids (glutamate, alanine), ammonium ion, energy store and mediators (ATP, ADP, AMP and creatine phosphate), and the energy charge potential were evaluated. Furthermore, in the crude extract and/or mitochondrial fraction of another portion of the same gastrocnemius muscle the maximum rate (Vmax) of some muscular enzymes related to the anaerobic glycolytic pathway (hexokinase, lactate dehydrogenase), the Kreb's cycle (citrate synthase, malate dehydrogenase), the aminoacid pool related to the Krebs' cycle (glutamate dehydrogenase and aspartate aminotransferase), the electron transfer chain (cytochrome oxidase) and NAD+/NADH exchanges (total NADH cytochrome c reductase) was evaluated. Some glycolytic metabolites and Krebs' cycle intermediates were modified by acute hypoxia, while free amino acids and energy mediators remained practically unchanged. The pharmacological treatment maintained the glucose and succinate muscular concentrations within the normal range, during hypoxia. The behaviour of muscular metabolites during hypoxia and/or post-hypoxic recovery is an age-related event. In fact, only in young-adult animals did the altered values return to normal in post-hypoxic recovery. In the present experimental conditions, only minor changes were observed as far as muscular enzyme activities are concerned. In any case, some enzyme activities tested showed different Vmax in young-adult dogs in comparison with mature ones.
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PMID:Effect of hypoxia, aging and pharmacological treatment on muscular metabolites and enzyme activities. 322 9

The enzymes of 35 adult Paragonimus uterobilateralis were analysed using thin-layer starch gel electrophoresis. From a total of 21 enzyme systems studied, 15 proved to be useful for the description and recognition of this species. All individuals were identical concerning 11 enzymes. In four remaining enzymes, alanine aminotransferase (ALAT, hexokinase, aspartate aminotransferase and phosphogluconate dehydrogenase, two or three variants, also being partly typical for this species were observed. In a comparison involving seven different enzymes, there were no differences between the electrophoretic patterns of 35 adult and 24 juvenile P. uterobilateralis. Additional examinations of 30 adult P. uterobilateralis with isoelectric focusing on ultrathin-layer polyacrylamide gels revealed clearer separations of enzymes. The method showed corresponding results or identiy of all individuals tested with three representative enzymes (ALAT, glucosephosphate isomerase and adenylate kinase).
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PMID:Isoenzymes of the lung fluke Paragonimus uterobilateralis from Liberia. 344 38

Human red blood cells were separated by a discontinuous Percoll density gradient into fractions of increasing density. Red cells comprising the lowest and highest density fractions, respectively, were subsequently separated according to mean cell volume (MCV) by means of counterflow centrifugation. The activities of 4 red cell age-dependent enzymes (hexokinase (HK), pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G6PD) and aspartate aminotransferase (ASAT) were highest in the red cell fraction with low density/large MCV, although the difference from red cell enzyme activities in the total low density fraction was not significant. These 4 enzyme activities were lowest in the fraction of red cells with high density/small MCV. The relative activities of the enzymes in the high density/small MCV fraction, as compared to the unseparated cell population, were: HK (58%), PK (49%), G6PD (53%) and ASAT (28%). These activities were all significantly lower than those measured in the total high density red cell fraction. The rates of lactate production in the low density/large MCV cells (0.89 +/- 0.15 mumol X min-1 X 10(-11) cells) is approximately 3-fold higher than in high density/small MCV cells (0.33 +/- 0.03 mumol X min-1 X 10(-11) cells). This latter value is 1.8-fold lower than the rate of lactate production in the total high density red cell fraction (0.59 +/- 0.14 mumol X min-1 X 10(-11) cells) and is, in contrast to lactate production in other density/size fractions, insensitive to phosphate as a metabolic stimulus. It is argued that the combination of density gradient and counter-flow centrifugation offers a greater potential for obtaining an old red cell population than classical red cell density centrifugation alone.
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PMID:Glycolytic activity in human red cell populations separated by a combination of density and counterflow centrifugation. Evidence for an improved separation of red cells according to age. 378 70

Activities of the red cell enzymes hexokinase, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, lactic dehydrogenase and aspartate aminotransferase were measured in 17 chronic haemodialysis patients receiving androgen therapy, 15 untreated chronic haemodialysis patients and 15 normal subjects. Compared to normal subjects, untreated haemodialysis patients had similar reticulocyte counts but significantly increased levels of all five enzymes studied. This finding suggests the presence of a younger red cell population in the peripheral blood and is consistent with the shortened red cell survival known to occur in this clinical setting. Red cell enzyme activities in untreated haemodialysis patients were significantly correlated with one another and with the serum phosphate level. Moreover, in this population, red cell DPG content was directly related to hexokinase and glucose 6-phosphate dehydrogenase activities while haemoglobin-oxygen affinity (P50) was inversely related to all five enzyme activities. In contrast, in androgen-treated haemodialysis patients, despite higher reticulocyte counts, red cell enzyme activities were the same or lower than those in the untreated haemodialysis group and only slightly higher than those in normal subjects, suggesting an overall older red cell population. Moreover, relationships of red cell enzymes to one another, to serum phosphate levels and to both red cell DPG content and haemoglobin-oxygen affinity were significantly different in androgen-treated subjects than in the untreated haemodialysis group. These changes are consistent with a direct effect of androgens on red cell metabolism and an improved red cell survival during androgen therapy.
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PMID:Androgen therapy in haemodialysis patients. II. Effects on red cell metabolism. 382 30


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