Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The acyl-CoA:sn-glycerol-3-phosphate acyltransferase (EC 2.3.1.15) (glycerol-P acyltransferase) and acyl-CoA:dihydroxyacetone phosphate acyltransferase (EC 2.3.1.42) (DHAP acyltransferase) activities were investigated in vitro in order to evaluate the quantitative contribution of the glycerol-P and DHAP pathways for the synthesis of triacylglycerols in isolated fat cells and to test the hypothesis that these two activities may be dual catalytic functions of a single enzyme. More than 85% of both acyltransferase activities was associated with the microsomal subcellular fraction. The microsomal glycerol-P acyltransferase activity showed an apparent Km of 8 muM for glycerol-P with a Vmax of 15.6 nmol/min/mg, while the DHAP acyltransferase activity showed an apparent Km of 40 muM for DHAP with a Vmax of 9.7 nmol/min/mg. Glycerol-P was a competitive inhibitor (Ki = 7.2 muM) of the DHAP acyltransferase, and DHAP was a competitive inhibitor (Ki = 92 muM) of the glycerol-P acyltransferase. The two acyltransferase activities showed virtual identity in their pH dependence, acyl-CoA chain length dependence, thermolability, and inactivation by N-ethylmaleimide. Trypsin, detergents, collagenase, phospholipases, and various salts and organic solvents also had similar effects on both activities. Taken as a whole, the data strongly suggest that the microsomal glycerol-P and DHAP acyltransferase activities actually represent dual functions of a single enzyme. Calculations based on the above kinetic constants and previously reported glycerol-P and DHAP pools in adipocytes suggest that the in vivo ratio of glycerol-P to DHAP acylation should be greater than 24:1.
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PMID:Triacylglycerol synthesis in isolated fat cells. Evidence that the sn-glycerol-3-phosphate and dihydroxyacetone phosphate acyltransferase activities are dual catalytic functions of a single microsomal enzyme. 0 98

Adipocytes were prepared by collagenase digestion of rat epididymal adipose tissue and incubated for 5, 15 or 30 minutes in Krebs-Ringer bicarbonate buffer containing albumin (40 mg/ml), glucose (1 mg/ml) and epinephrine. Calcium ion was present in some incubations at concentration of 2.5 mM and omitted from others; media with no added calcium contained 1.0 mM EGTA thereby producing a final calcium concentration of less than 10(-7) M. Glycerol release and accumulation of cyclic AMP were measured. Basal lipolysis and cell cyclic AMP levels were increased slightly but not significantly when adipocytes were incubated in calcium free media. Lipolysis could be activated with epinephrine in the absence of calcium but the sensitivity of the lipolytic response was greatly reduced; however, the maximum lipolytic response to epinephrine was not decreased in calcium free media. Similarly, incubation of adipocytes in calcium free media resulted in decreased accumulation of cyclic AMP in response to epinephrine but only when sub-maximum concentrations of the catecholamine were present. Varying the extracellular calcium concentration showed that a concentration of at least 10(-5) M was optimal for epinephrine activation of lipolysis. These observations are considered in accord with the view that activation of adenylate cyclase is facilitated by calcium ion.
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PMID:The role of calcium ion in epinephrine activation of lipolysis. 18 5

It has been shown that adipose tissue lipolytic activity is increased in endurance-trained subjects. In women, adipose tissue is extensive and it was thought interesting to confirm that endurance training increases the capacity of female adipose tissue to mobilize lipids, and moreover to more fully understand the mechanisms involved. So, biopsies of fat were obtained from the periumbilical region of 13 trained female runners (T) and 17 sedentary women (S) and the in vitro response to catecholamines of the collagenase-isolated fat cells was studied. Glycerol release, chosen as adipocyte lipolysis indicator, was measured by bioluminescence for various epinephrine and norepinephrine concentrations. In both groups, these substances provoked an increase in lipolysis, but the response was significantly higher in T. In both groups, isoproterenol increased the lipolytic activity above basal concentrations at 10(-8) M and above. Lipolytic activity in T was significantly higher (P less than 0.01) than the S control at 10(-7) M and above. Epinephrine plus propranolol decreased lipolysis in both groups, but at 10(-5) M, lipolytic activity was significantly lower in S than in T (P less than 0.05). It is concluded that in female subjects, endurance training increases the sensitivity of subcutaneous abdominal adipose tissue to the lipolytic action of catecholamines; this effect seems to be related both to a decreased efficiency of the alpha 2-adrenergic pathway and to an increased efficiency of the beta-adrenergic pathway. This latter effect seems to take place at a step beyond the receptor-adenylate cyclase system in the lipolytic cascade.
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PMID:Lipolytic response of fat cells to catecholamines in sedentary and exercise-trained women. 253 83

Adipose tissue lipolytic activity is increased in endurance-trained subjects, but little is known about the mechanisms of this increase. To understand more fully the mechanisms involved and to discover whether sex-related differences exist, biopsies of fat were performed in the periumbilical region of 20 sedentary subjects (10 women (W) and 10 men (M)) and 20 trained subjects (10 W, 10 M); the in vitro response to epinephrine of the collagenase-isolated fat cells was studied. Glycerol release, chosen as an adipocyte lipolysis indicator, was measured by bioluminescence. Dose-response curves with epinephrine (alpha 2 and beta agonist), with isoproterenol (beta agonist) and epinephrine + propranolol and adenosine deaminase, were studied. Epinephrine-induced lipolysis was enhanced in trained subjects and this was due to an increased efficiency of the beta-adrenergic pathway. However, differences were found between the two sexes. In trained men, the lipolysis increase resulted from the enhancement of the beta-adrenergic pathway efficiency without any significant decrease in the alpha 2-adrenergic pathway efficiency. In trained women, the lipolysis increase was not only due to the enhancement of the beta-adrenergic pathway efficiency (which was greater than in trained men), but also to a significant decrease in the alpha 2-adrenergic pathway efficiency. Despite the decrease, the alpha 2-adrenergic pathway remained more efficient in trained women than in trained men, as was the case in sedentary subjects. It is concluded that endurance training led to better lipid mobilization and that this effect seemed greater in women than in men.
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PMID:Lipolytic response of adipocytes to epinephrine in sedentary and exercise-trained subjects: sex-related differences. 258 71

Endurance training helps muscle tissue oxidize lipids and therefore helps conserve glycogen. It was thought interesting to find out if, in addition to this preferential use of fatty acids by muscle tissue, there is an increase in the capacity of adipose tissue to mobilize lipids. So the response to epinephrine of collagenase-isolated fat cells obtained after biopsies of fat performed in the periumbilical region of 10 trained marathon runners (T) and 10 sedentary subjects (S), all males, was studied in vitro. Glycerol release, chosen as adipocyte lipolysis indicator, was measured by bioluminescence. Lipolysis was studied with increased epinephrine concentration. This caused a significant increase in lipolysis only in the T subjects. The dose-response curves were significantly different for T and S subjects at 10(-6) M and above (P less than 0.05). To determine the modification mechanisms observed, lipolysis with isoproterenol and epinephrine plus propranolol were studied. Isoproterenol significantly increased lipolysis in both groups. The dose-response curves were significantly different at 10(-7) M (P less than 0.01) and above. In both groups, epinephrine plus propranolol significantly decreased lipolysis without distinction between T and S. It is concluded that in male subjects endurance training increases the sensitivity of subcutaneous abdominal adipose tissue to the lipolytic action of epinephrine; this effect seems to be related to an increased response of the beta-adrenergic pathways.
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PMID:Effect of physical training in humans on the response of isolated fat cells to epinephrine. 373 12

Glycerol and dihydroxyacetone are metabolized by rabbit kidney-cortex tubules, isolated by collagenase treatment. Half-maximal concentrations of both substrates were determined with regard to uptake rates and product formations. Maximal uptake rates were 643 and 329 mumol/h per g of protein for dihydroxyacetone and glycerol respectively. Glucose and lactate were found as major metabolic products. Glycerol kinase, the enzyme catalysing the first step in renal glycerol and dihydroxyacetone metabolism, was measured radiochemically as described by Newsholme, Robinson & Taylor [(1967) Biochim, Biophys. Acta 132, 338-346] and adapted for studies of the localization of this enzyme along the different structures of rabbit nephron. The results show that glycerol kinase is located exclusively in the proximal segments, i.e. the proximal convoluted tubules and the pars recta, but is negligible in the other structures studied. The activities were close to the maximal dihydroxyacetone uptake rates measured in tubule suspensions.
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PMID:Renal glycerol metabolism and the distribution of glycerol kinase in rabbit nephron. 627 52

We hypothesized that exposure to tumor necrosis factor-alpha (TNF-alpha) would significantly increase lactate production by adipose-tissue (AT) fragments and isolated adipocytes. We therefore examined the effects of TNF-alpha on the metabolism of epididymal AT explants during 24-hour tissue incubation. We also studied the effects of this 24-hour TNF-alpha tissue exposure on subsequent glucose metabolism and lipolysis by isolated adipocytes. Glycerol release into the medium was significantly increased (50%, P =.027) by exposure of the AT fragments to TNF-alpha (4 nmol/L) for 24 hours. During this time, glucose uptake from the medium and lactate release into the medium tended to increase, whereas leptin release into the medium tended to decrease, but these effects of TNF-alpha were not statistically significant. After the 24-hour AT-explant incubation, adipocytes were isolated by means of collagenase digestion from the AT fragments and subsequently tested in a short-term (60-minute) metabolic incubation. Prior exposure to TNF-alpha resulted in a significant increase in adipocyte glycerol release (P =.044), total glucose metabolism (P =.019), and lactate production (P =.037). With the exception of lactate, TNF-alpha produced no significant stimulation of the metabolites of glucose. The pattern of glucose metabolism elicited by TNF-alpha exposure differs from that usually attributed to a lipolytic hormone and suggests that the effects of TNF-alpha on glucose metabolism involve pathways separate from, or in addition to, its effects on lipolytic stimulation.
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PMID:Effects of TNF-alpha on glucose metabolism and lipolysis in adipose tissue and isolated fat-cell preparations. 1194 24

Many procedures have been described for rat pancreatic islet isolation. Several factors contribute to the pancreatic islet isolation outcome. One of the main problems in islet isolation procedure is the formation of a viscouse, gellike structure during collagenase digestion which entraps the free islets and decrease islet yield after density gradient purification. This issue has not been addressed in most techniques described for rat islet isolation. We examined effect of various factors to eliminate formation of gellike material and improve the islets yields. Islet isolation was performed on 26 adult male Wistar Albino rats weighing between 280 and 350 g. We have observed that several factors affect pancreatic islet isolation. Optimum Collagenase enzyme concentration, maintaining pH range between 7.7 and 7.9 in digestion solution, incubation temperature at 38+/-1 degrees C and addition of Calcium ion decreased the formation of gellike materials and increased islet yield. Addition of Glycerol as a gelatin solvent has also been helpful in the reduction or complete elimination of gellike material. Precise optimization of rat islet isolation procedure is useful to improve the islet yield in islet transplantation studies.
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PMID:Optimizing conditions for rat pancreatic islets isolation. 1900 33

Glycerol and xylitol hydrate the skin and improve its barrier function over a short period. We studied the effects of glycerol and xylitol on the physiological properties and morphology of the skin after longer-term application. Twelve volunteers with dry skin were examined. Three areas on the arms were determined. Area 1 served as untreated control. The vehicle was applied to area 2, while area 3 was treated twice daily with a formulation containing glycerol (5%) and xylitol (5%) for 14 days. Transepidermal water loss (TEWL), hydration and biomechanical properties of the skin were monitored. Biopsies were taken for routine histology and immunohistochemistry for filaggrin and matrix metalloproteinase-1 (MMP-1). The polyols increased the skin hydration and protein quantity of filaggrin, elevated the interdigitation index, decreased the TEWL and improved the biomechanical properties of the skin, but did not change the protein expression of MMP-1. A combination of glycerol and xylitol can be useful additional therapy for dry skin.
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PMID:Effects of Locally Applied Glycerol and Xylitol on the Hydration, Barrier Function and Morphological Parameters of the Skin. 2734 97