Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Noradrenaline-storing granules, a mitochondrial fraction and a microsomal fraction of bovine splenic nerve trunks were prepared by differential centrifugation. These particulate fractions were characterized by their noradrenaline content, succinate dehydrogenase and glucose-6-phosphatase activity. In the presence of ATP-Mg2+ all three fractions accumulated 45Ca2+ during incubation with 0.1 mM 45 CaCl2, buffered with potassium phosphate or glycylglycine (pH 7.5; 28 degrees C). The accumulated 45 Ca2+ was not removable by EGTA, and the uptake was absent at 0 degrees C or after destruction of the particles by sonication. The behaviour of the 45 Ca2+ -uptake into all three fractions against varying ATP-concentrations, metabolic inhibitors (pentachlorophenol, desaspidine, 2,4-dinitrophenol, N-ethylmaleimide, p-chloromercuribenzoate, sodium azide, amobarbital) and drugs (phenoxybenzamine, verapamil, prenylamine, reserpine, bretylium, phentolamine) was studied. Under nearly all conditions there were differences between the 45 Ca2+ -uptake into mitochondria and that into microsomes, which suggests two distinct uptake processes. The 45 Ca2+ -uptake into the granule fraction behaved intermediate between the two other fractions under many conditions, but not under all. Therefore, it is not possible to explain the 45 Ca2+ -uptake into the granule fraction as being due to contamination with mitochondria and microsomes; an inherent ATP-Mg2+ -dependent 45Ca2+ -uptake into the nerve granules must be postulated, which is not directly coupled with the noradrenaline transport into these particles. A particulate fraction (14000-100000 g), containing noradrenaline granules, was prepared from the vas deferens of the rat. Incubation with 5 X 10(-6) M (-)-noradrenaline and 0.1 mM 45Ca2+ showed that the particles of this fraction take up noradrenaline and 45Ca2+. The uptake of both was dependent on ATP-Mg2+. The ATP-Mg2+ -dependent uptake of both noradrenaline and 45Ca2+ was substantially reduced in the corresponding tissue fraction prepared from denervated vasa deferentia.
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PMID:Ca2+ -uptake into noradrenaline-storing granules of bovine splenic nerves. 18 27

It has recently been reported that free Ca2+, a second hormonal messenger in the liver, can modulate the activity of liver glucose-6-phosphatase by inhibition (van de Werve, G. (1989) J. Biol. Chem. 264, 6033-6036) or activation (Yamagushi, M., Mori, S., and Suketa, Y. (1989) Chem. Pharm. Bull. (Tokyo) 37, 388-390). Such a controversial role for Ca2+ is reinvestigated by comparing the effect of the addition of free Ca2+ (10(-10) to 20.10(-3) M) under the form of CaCl2 or of Ca-EGTA buffers. We show that the glucose-6-phosphatase activity is: 1) increased in the presence of CaCl2 at concentrations higher than 10(-4) M and unaffected in the presence of CaCl2 at lower concentrations; 2) decreased in the presence of Ca-EGTA buffers yielding free Ca2+ concentrations higher than 10(-8) M; 3) the latter effect is not depending on free Ca2+ or free EGTA concentrations, but on Ca.EGTA complex concentration. In addition, these effects can be reproduced in the same concentration ranges by MgCl2 and Mg-EDTA buffers, respectively. It is concluded that a physiological role for free Ca2+ on the activity of liver glucose-6-phosphatase remains to be established.
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PMID:Reappraisal of the effect of Ca2+ on the activity of liver microsomal glucose-6-phosphatase. 215 96

Calcium uptake and binding activities of microsomal fractions from bovine coronary artery and aorta were examined. The isolated microsomal fraction of the coronary artery and aorta showed 7- to 8-fold higher glucose-6-phosphatase activity and 4- to 6-fold higher NADPH-cytochrome c reductase activity as compared with the corresponding values for the homogenate fraction. Coronary artery and aorta microsomal calcium uptake activities were 118 and 159 nmoles Ca2+/mg protein/10 min in the presence of 100 microM CaCl2, respectively. These activities for bovine vascular smooth muscle microsomes are higher than those of other species investigated. The calcium uptake activities were dependent on calcium concentrations ranging from 5 to 50 microM in the assay medium. The onset of the reaction for aorta microsomal calcium uptake was faster than that for the coronary artery. The calcium uptake activity was also dependent on ATP, but it was practically independent of oxalate ions in the assay medium. Microsomal calcium binding activities of the coronary artery and aorta were maximal at 20 min of incubation under the present experimental conditions. A lower Km value of the aortic calcium binding for ATP was obtained as compared with that for the coronary artery. The present experiment explored several characteristics of the microsomal calcium-accumulating ability of vascular smooth muscle, which provides meaningful information for further study on cellular calcium movements in vascular smooth muscle.
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PMID:Microsomal calcium-accumulating ability of bovine coronary artery and aorta. 299 Apr 86