Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pathways of adenine nucleotide catabolism were investigated in cultured beating cardiomyocytes. The activity of the enzymes involved in AMP degradation was assayed in cell extracts. Fluxes of label from ATP to the various purine derivatives were measured in intact cells. Under physiological conditions, cells degraded AMP through deamination to IMP. IMP was rapidly degraded to inosine, hypoxanthine, xanthine and uric acid, which were effluxed from the cells. This is in accord with the fact that the activity of AMP deaminase (EC 3.5.4.6) was 7-fold that of AMP 5'-Nucleotidase (EC 3.1.3.5). Mild ATP-degradation, induced by inhibition of glycolysis by iodoacetate, caused no alterations in the degradation pathways (more than 85% through deamination to IMP). However, fast ATP-degradation (83% of adenine nucleotides/10 min), induced by simultaneous inhibition of glycolysis and electron transport (by antimycin A), caused increased dephosphorylation of AMP to adenosine (50% of total AMP-degradation). The cardiomyocyte extracts were found to contain a significant activity of purine nucleoside phosphorylase (EC 2.4.2.1). Despite the presence of hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8), salvage of hypoxanthine to IMP, both at physiological as well as at conditions associated with ATP degradation, was slow. The salvage of adenosine appeared to be efficient at physiological conditions, but not at fast rates of ATP degradation.
J Mol Cell Cardiol 1988 Jan
PMID:Pathways of adenine nucleotide catabolism in primary rat cardiomyocyte cultures. 325 63

In order to study the role of elastin in arteries with respect to hypertension and hypertensive arterial disease, aortic elastin content and elastase-like enzyme activity were examined and compared in stroke-prone spontaneously hypertensive rats (SHRSP), which show malignant hypertension, and Wistar-Kyoto normotensive rats (WKY). The elastin content was lower, whereas the elastase-like activity was higher at 20 weeks of age in SHRSP than in WKY, so that the aortic elastin/enzyme ratio of SHRSP was lower than that in WKY. These differences were not found at 6 weeks of age (prehypertensive stage). For SHRSP anti-hypertensive treatment resulted in lowering the elastase-like activity and in increasing the elastin content in comparison to untreated animals. The subcellular distribution of the elastase-like activity closely correlated with that of 5'-nucleotidase activity, a plasma membrane marker enzyme. The results indicate involvement of a smooth muscle plasmalemmal elastase-like enzyme in vascular connective tissue metabolism in health and possibly also its participation in hypertensive arterial diseases.
Exp Mol Pathol 1987 Aug
PMID:Elastin and elastase-like enzyme change in aorta of rat with malignant hypertension. 364 94

Homogenates of control and diet-induced atherosclerotic aortas of rabbit were prepared and the levels of DNA, protein, free and esterified cholesterol, and six enzymes known to be associated with various subcellular organelles [N-acetyl-beta-glucosaminidase, beta-galactosidase (lysosomes); cytochrome oxidase (mitochondria); neutral alpha-glucosidase (endoplasmic reticulum); 5'-nucleotidase (plasma membrane); catalase (peroxisomes)] were compared between control and atherosclerotic preparations. The levels of prostaglandins I2, E2, and F2 alpha, based on DNA, also were measured by radioimmunoassay. Atherosclerotic aortas were significantly enriched in catalase activity (440%) and in each of the acid hydrolases (395 and 630%), based on DNA, as well as in free (630%) and esterified cholesterol (930%), based on tissue wet weight, compared to control aortas. The control level of prostaglandin I2 was 10-fold higher than that of prostaglandin E2, which was 3-fold higher than that of prostaglandin F 2 alpha. Prostaglandin I2 doubled in amount with advanced atherosclerosis, while prostaglandin E2 increased over 10-fold, resulting in twice the amount of prostaglandin I2 than E2 in advanced atherosclerosis; the level of prostaglandin F2 alpha did not appear to change significantly with atherosclerosis. Increased levels of prostaglandins I2 and E2 were correlated significantly with increased aortic total cholesterol content (based on DNA) but not increased serum cholesterol levels. N-Acetyl-beta-glucosaminidase activity also was correlated significantly to aortic total cholesterol content and beta-galactosidase activity, as well as to the level of prostaglandin I2; in contrast, N-acetyl-beta-glucosaminidase was not significantly correlated to prostaglandin E2. The association of prostaglandins I2 and E2 with aortic total cholesterol suggests the participation of prostaglandins in the response of arterial cells to lipid accumulation in atherosclerosis. The specific association of aortic prostaglandin I2 level and N-acetyl-beta-glucosaminidase activity further suggests a possible role for this prostaglandin during arterial intralysosomal cholesterol accumulation.
Exp Mol Pathol 1985 Aug
PMID:Arterial prostaglandins and lysosomal function during atherogenesis. I. Homogenates of diet-induced atherosclerotic aortas of rabbit. 389 3

Small (15-18 microns) and large (18-45 microns) luteal cells were obtained from bovine corpora lutea of pregnancy by centrifugal elutriation of enzymatically dispersed luteal cells. Small luteal cells accounted for about 85% and large luteal cells for 8-12% of total luteal cell population. Small luteal cells were characterized by a low cytoplasmic/nuclear ratio with cytoplasm containing mitochondria, lysosomes, lipid droplets, dense granules and endoplasmic reticulum. Large luteal cells possessed a higher cytoplasmic/nuclear ratio with cytoplasm containing more abundant mitochondria, lipid droplets, dense granules and lysosomes compared to small luteal cells. Some of the mitochondria were very long. Both small and large luteal cells contained scarce amounts of Golgi elements. Dense granules were found close to the nucleus in both cell types. The nucleus of both cell types was acentric, irregular in shape and contained a well-defined nucleolus. The highly condensed chromatin in small luteal cells was found at the nuclear periphery and in the central region. Dispersed chromatin was found throughout the nucleus with condensed chromatin at the nuclear periphery of large luteal cells. Macrophages and fibroblasts were occasionally found in small luteal cell preparations, but their morphology was quite distinct from both small and large luteal cells. Scanning electron microscopy revealed that the majority of the small and large luteal cells were spherical or slightly elongated in shape. Small luteal cells displayed the presence of blebs, ruffles and short microvilli. Large luteal cell surface contained ruffles and randomly distributed clusters of blebs of different sizes, predominantly spherical in shape with a smooth surface. Finger-like projections were also occasionally seen. Small luteal cells contained significantly lower amounts of protein, but the ratios between protein and DNA were similar in both cell types. The basal, human chorionic gonadotropin (hCG)- or cyclic AMP-stimulated progesterone production, the apparent dissociation constants for [125I]hCG binding and the apparent total number of available sites per cell were similar in small and large luteal cells. The activities of enzymes that are involved directly or indirectly in progesterone biosynthesis and those involved in general cellular metabolism and biosynthesis were also similar in small and large luteal cells with one exception. That is, the activities of 5'-nucleotidase and NADH cytochrome c reductase were significantly higher in small compared to large luteal cells.
Mol Cell Endocrinol 1984 Aug
PMID:Morphological and biochemical characterization of small and large bovine luteal cells during pregnancy. 608 29

Thyrotropin given to support-anchored cultures of porcine thyroid cells, either in a serum-containing or in a serum-free system, produced an increase of about 50% in the total activity of 5'-nucleotidase. In the serum-free culture, in which TSH was administered to well-reformed follicles, this increase in 5'-nucleotidase activity concerns both the ecto-enzymic and intracellular forms of the enzyme and it coincides with the period of several days during which several glycosyltransferase activities are elevated and thyroglobulin production increased. Taken together, and in view of a recent in vitro study (Brandan and Fleisher, 1982) documenting the fate of uridine diphosphate in Golgi vesicles, these results suggest that there might be a functional correlation between the stimulation of 5'-nucleotidase and an increased production of nucleoside mono- and diphosphates when the activity of a number of glycosyltransferases is increased.
Mol Cell Endocrinol 1984 Oct
PMID:Thyrotropin increases 5'-nucleotidase activity in primary cultures of porcine thyroid cells. 609 84

Microvillous membranes isolated from early gestation placentas (8-12 weeks of amenorrhoea) and from mid-term placentas (20-22 weeks of amenorrhoea) were used to study the specific binding of low-density lipoprotein (LDL) to the trophoblast. The purity of the microvillous preparations has been assessed by electron microscopy and by their enrichment in two membrane markers, 5'-nucleotidase and alkaline phosphatase. Evidence was presented demonstrating the existence of saturable binding sites for [125I]LDL in placental microvilli as early as 6 weeks of pregnancy. The apparent KD values for these binding sites have been determined by Scatchard analyses to be 6.98 +/- 0.83 and 6.57 +/- 0.81 micrograms protein LDL/ml, for early gestation and mid-term preparations, respectively. This apparent KD value was unaffected by a pretreatment of the membranes by heparin, as indicated by the mean values of 7.13 +/- 0.89 and 6.97 +/- 0.75 micrograms protein LDL/ml obtained for immature microvilli preincubated with or without heparin, respectively. Large variations of binding capacity were observed in each gestational age group and no significant difference was found between them. These results indicate that the LDL binding sites of the human placenta, located on the microvillous membranes, (i) are present as early as the 6th week of pregnancy, and (ii) display the same high affinity and specificity for LDL as those of the term trophoblast.
Mol Cell Endocrinol 1984 Dec
PMID:Low-density lipoprotein binding sites in the microvillous membranes of human placenta at different stages of gestation. 609 85

The gamma-glutamyltransferase (gamma-GT) activity decreased by 50% following adrenalectomy of female rats, in homogenate as well as in a purified plasma membrane preparation from liver. In contrast, such a variation was not found in the kidney. None of 3 other enzyme activities of the plasma membrane, namely 5'-nucleotidase, alkaline phosphatase, and alkaline phosphodiesterase I, was decreased by adrenalectomy. Administration of hydrocortisone (5 mg/100 g body weight) resulted in a 2.6-fold increase in hepatic gamma-GT activity from adrenalectomized rats. The hydrocortisone-mediated stimulation of gamma-GT activity was dose- and time-dependent. The 5'-nucleotidase and leucine aminopeptidase activities were not modified by the hydrocortisone treatment. The activity of gamma-GT was mainly associated with nuclear fractions (nuclei and plasma membranes) obtained from liver homogenates of either control, adrenalectomized or adrenalectomized hydrocortisone-treated animals, and this activity was purified 18-fold in a plasma-membrane preparation as compared to homogenate. These data suggest that adrenalectomy and conversely hydrocortisone treatment modulate specifically the hepatic plasma-membrane gamma-GT activity. This represents one of the first demonstrations of a specific modulation by glucocorticoids of an enzyme activity typical of the plasma membrane.
Mol Cell Endocrinol 1980 May
PMID:In vivo modulation of rat hepatic gamma-glutamyltransferase activity by glucocorticoids. 610 52

Pyrophosphate, p-nitrophenyl phosphate and a variety of pyrimidine and purine nucleotides are hydrolyzed by the solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. The pH optima (or ranges) for hydrolysis of substrates are 8.0 (pyrophosphate), 8.8 (p-nitrophenyl phosphate), 8.4-8.9 (nucleoside monophosphates), and 7.1-8.1 (nucleoside triphosphates); all substrates, with the exception of nucleoside triphosphates, have a higher affinity for the solubilized enzyme at pH 7.4 than at their optimal pH for hydrolysis. ATP is degraded completely by the enzyme preparation to adenosine and inorganic phosphate, but since neither ADP nor ATP accumulate in the incubation medium it is not known whether ATP hydrolysis involves the sequential hydrolysis of terminal phosphate groups. Isoelectric focusing and various chromatographic procedures (gel permeation, ion-exchange and hydrophobic interaction chromatography) fail to separate the alkaline phosphatase, phosphodiesterase, 5'-nucleotidase, adenosine triphosphatase and ribonuclease activities associated with the solubilized membrane preparation. Additionally, inhibitor studies indicate that only a single enzyme with low substrate specificity is involved in the hydrolysis of nucleotides, p-nitrophenyl phosphate, pyrophosphate and hexose phosphate esters. Purines and pyrimidines and their nucleosides interact with the active site, and in some instances activity of the enzyme is stimulated by an unknown mechanism.
Mol Biochem Parasitol 1983 May
PMID:Nucleotide hydrolysis by solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. 613 88

In this study we have attempted to correlate reversible and irreversible cell damage induced by in vivo or in vitro ischemia with characteristics of the plasma membranes of liver parenchymal cells, as detected biochemically and ultrastructurally. The effects of in vivo or in vitro ischemia appeared to be similar. It was virtually impossible to isolate a substantial membrane fraction from ischemic livers, probably because of changes in the physical properties of the membranes by ischemia. The isolated membranes of ischemic liver cells show ultrastructural changes including the occurrence of many vesicular profiles and alterations in junctional complexes expressed by extended and smudged electron densities along the lateral surfaces. The microvilli of the bile canaliculi disappeared after only 15 min ischemia and cytoplasmic densities associated with junctional complexes also appeared extended and smudged. These changes correspond with the alterations observed in ischemic isolated membranes. After 30 min in vivo ischemia the activity of 5'-mononucleotidase used as a marker enzyme for plasma membranes, decreased by 75%, whereas the activity of thymidine 5'-phosphodiesterase was reduced only slightly. The changes in these enzyme activities were more prominent after in vitro ischemia than after in vivo. The morphological and biochemical changes observed in rat hepatocyte plasma membrane during the early stage of injury have no value in predicting the occurrence of necrosis in a later phase of the process since profound changes occur in plasma membrane properties after even short periods of ischemia (i.e. during the reversible stage).
Virchows Arch B Cell Pathol Incl Mol Pathol 1984
PMID:Biochemical and ultrastructural changes in rat liver plasma membranes after temporary ischemia. 615 May 74

The endoplasmic reticulum (ER) of MPC-11 cells released as vesicles upon cell disruption by nitrogen cavitation was separated from the bulk of mitochondria, lysosomes and plasma membranes by a low speed centrifugation. The ER membranes were fractionated on discontinuous sucrose gradients into heavy rough (HR), light rough (LR) and smooth (S) membranes. The morphology of subcellular fractions was studied by electron microscopy and the ER membranes were shown to be virtually free of contaminating organelles. The S fraction was easily distinguishable because of the lack or ribosomes but there were no apparent morphological differences between the HR and LR fractions. Of total activity in the microsomal subfractions, 70% of the UDPase and 67% of the 5'-nucleotidase activity was associated with the S fraction. Polysomes were present in the HR, LR and nuclear-associated ER fractions but not in the S fraction. The HR and LR fractions did not appear to be contaminated to any great extent with free polysomes. RNA/protein and RNA/phospholipid ratios of the HR fraction were higher than those of the LR fraction, indicating a greater density of ribosomes in the former fraction. These ratios were much lower in the S fraction reflecting the low ribosome content.
Mol Cell Biochem 1981 Feb 11
PMID:Ultrastructure and polysome content of the microsomal subfractions of mouse plasmacytoma cells. 616 58


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