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

The subcellular origin of membranes from rat skeletal muscle that contain insulin-responsive glucose transporters was investigated. Rat skeletal muscle membranes were prepared by isopycnic centrifugation in sucrose gradients. In vivo insulin treatment increased the content of GLUT-4 glucose transporters in the 25% sucrose fraction (enriched in the plasma membrane marker 5'-nucleotidase) and decreased it in the 35% sucrose fraction (devoid of plasma membrane markers). The possibility of endothelial cell membrane contamination in these fractions was investigated using a mouse monoclonal antibody, MRC OX-43, raised against a cell surface protein specific to rat vascular endothelium. MRC OX-43 did not react with any of the muscle membrane fractions, but did recognize a protein of around 100 kDa in extracts of human endothelial cells and rat aorta. An antibody to the dihydropyridine receptor of skeletal muscle, IIC12, was used to determine the presence of transverse tubules in these fractions. IIC12 reacted positively with a 180-kDa protein in purified rat transverse tubules. In contrast, this antibody did not cross-react with the 25% or 35% sucrose fractions. The 25% sucrose fraction was devoid of calsequestrin and ryanodine receptor, cisternal sarcoplasmic reticulum markers. However, small amounts of these proteins were detected in the 35% sucrose fraction. The results suggest that the 25% sucrose fraction represents plasma membranes, while the 35% sucrose fraction is an insulin-sensitive intracellular fraction that contains, but is not enriched in, sarcoplasmic reticulum cisternae. The results further show that insulin-induced recruitment of GLUT-4 transporters in skeletal muscles can be demonstrated independently of GLUT-4 recruitment in endothelial cells.
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PMID:Characterization of glucose transporter-enriched membranes from rat skeletal muscle: assessment of endothelial cell contamination and presence of sarcoplasmic reticulum and transverse tubules. 198 44

Recent studies have provided evidence for a role of cyclic ADP-ribose (cADPR) in the regulation of intracellular calcium in smooth muscles of the intestine, blood vessels and airways. We investigated the presence and subcellular localization of ADP-ribosyl cyclase, the enzyme that catalyzes the conversion of beta-NAD(+) to cADPR, and cADPR hydrolase, the enzyme that degrades cADPR to ADPR, in tracheal smooth muscle (TSM). Sucrose density fractionation of TSM crude membranes provided evidence that ADP-ribosyl cyclase and cADPR hydrolase activities were associated with a fraction enriched in 5'-nucleotidase activity, a plasma membrane marker enzyme, but not in a fraction enriched in either sarcoplasmic endoplasmic reticulum calcium ATPase or ryanodine receptor channels, both sarcoplasmic reticulum markers. The ADP-ribosyl cyclase and cADPR hydrolase activities comigrated at a molecular weight of approximately 40 kDa on SDS-PAGE. This comigration was confirmed by gel filtration chromatography. Investigation of kinetics yielded K(m) values of 30.4+/-1.5 and 695. 3+/-171.2 microM and V(max) values of 330.4+/-90 and 102.8+/-17.1 nmol/mg/h for ADP-ribosyl cyclase and cADPR hydrolase, respectively. These results suggest a possible role for cADPR as an endogenous modulator of [Ca(2+)](i) in porcine TSM cells.
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PMID:Subcellular localization of cyclic ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase activities in porcine airway smooth muscle. 1104 51

The present study was conducted to investigate the effects of long-term exercise training on the main components involved in excitation-contraction coupling and relaxation in rat myocardium. Twenty male Wistar rats were divided into sedentary (S) and treadmill-trained (T) groups. Group T was trained for 24 weeks, 5 days/week (25 m/min, 45-60 min, 0% slope). 48 h after the last exercise session, animals were killed and ventricular and soleus muscle homogenates were obtained. The citrate synthase activity in soleus muscle was significantly increased (163%) in T compared with S rats ( P<0.01), confirming the exercise training efficacy. Although heart weight and cardiac oxidative capacity were not modified by exercise training, the binding of [(3)H] ryanodine and the dihydropyridine [(3)H]PN200-110 to cardiac homogenates, and sarcoplasmic reticulum Ca(2+)-ATPase activity were increased significantly in the ventricular homogenates from T compared with S animals ( P<0.01). Western blot analysis of ventricular homogenates failed to show significant alterations in dihydropyridine receptor and Ca(2+)-ATPase levels in T animals, but revealed an increase of ryanodine receptor density in this group ( P<0.01). The activity of the ectoenzymes 5'-nucleotidase and Mg(2+)-ATPase was not affected by training ( P>0.05). In conclusion, long-term treadmill training induces adaptive changes in some of the components of myocardial rat excitation-contraction coupling and relaxation systems that could contribute to the improvement of cardiac function.
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PMID:Ca2+ regulatory systems in rat myocardium are altered by 24 weeks treadmill training. 1273 53