Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.5 (neuropathy target esterase)
 1,070 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The positional specificity of the phospholipase A (EC 3.1.1.4) in human gallbladder epithelium has been studied using 14C-phosphatidylethanolamine radiolabeled either in the 1-acyl or in the 2-acyl position. After heating of homogenized epithelial cells at 70 degrees C for 2 min, their lysophospholipase activity was lost. In contrast, the ability to hydrolyze 14C-phosphatidylethanolamine in biosynthetically radiolabeled Escherichia coli was largely retained. The amounts of radioactivity found in the products of hydrolysis under different conditions suggest that there are two different phospholipase A activities in the gallbladder epithelium: one, with optimal activity at pH 7, that requires Ca2+ and is specific for the 2-acyl position, and another, with optimal activity at pH 4, that does not require Ca2+ and that, apart from the 2-acyl position, attacks the 1-acyl position as well. It is possible, therefore, that a complete deacylation of diacylphosphoglycerides in the gallbladder wall is brought about in two different ways: at neutral pH through a combined action of phospholipase A2 and lysophospholipase, the latter being able to hydrolyze the 1-acyl-lysophosphoglyceride, and, at acid pH, through the action of phospholipase A1 and A2 activity, presuming 1-acyl- and 2-acyl-lysophosphoglycerides are also attacked. Both these processes have to be considered in order to explain a turnover of diacylphosphoglycerides that physiologically would prevent the accumulation of lytic lysophosphoglycerides. The possible relevance of these findings to the pathogenesis of aseptic cholecystitis is inferred.
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PMID:The prerequisites for local lysolecithin formation in the human gallbladder. III. Demonstration of two different phospholipase A activities. 3 26

The subcellular localization of lysophospholipase activity in the human gallbladder epithelium was studied by differential and density gradient centrifugation. The highest relative specific activity was found in the microsomal fraction, although the enzyme appeared in mitochondria and lysosomes as well. The cytosol did not contain any significant lysophospholipase activity, but large amounts of enzyme were solubilized during centrifugation in sucrose gradients. These findings are discussed in relation to the distribution and properties of lysophospholipase in other cells and tissues and with regard to physiological implications. The possible relevance to the pathogenesis of aseptic cholecystitis is inferred.
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PMID:The biochemical prerequisites for preventing pathogenic lysolecithin activity in the human gallbladder. II. Studies on the subcellular localization of lysophospholipase. 63 41

The positional specificity of the phospholipase A in human gallbladder epithelium was studied by using biosynthetically radioabeled diacylphosphoglycerides as substrates. Diacylphosphoglyceride in 14C-palmitic acid-labeled, autoclaved E.coli was hydrolyzed under the formation of monoacylphosphoglyceride and fatty acid that were both radiolabled. In contrast, diacylphosphoglyceride in 14C-oleate-labeled bacteria was hydrolyzed so as to give radiolabel in the fatty acid only. Since 14C-palmitate occupies predominantly the 1-acyl position and 14C oleate the 2-acyl position of the major E. coli diacylphosphoglycerides, these findings suggest that: 1) the phospholipase attacks and 2-position of diacylphosphoglycerides, and 2) a complete deacylation of diacylphosphoglycerides in the gallbladder wall is brought about by the combined action of phospholipase A2 and lysophospholipase, the latter being able to hydrolyze the 1-acyllysophosphoglyceride. It appears, therefore, that the biochemical preequisites for a local formation and degreadation of lysolecithin in the gallbladder itself are met by the positional specificity of theenzymes present. This finding further substantiates the hypothesis that lysolecithin is an adjustable mediator of aseptic cholecystitis.
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PMID:The prerequisites for local lysolecithin formation in the human gallbladder. II. Studies on the positional specificity of the phospholipase A activity. 67 50

Human gallbladder epithelium was disintegrated to complete loss of microscopic structure and incubated at 37 degree C together with unlabelled lysolecithin and 14C-lysolecithin. During each incubation lysolecithin was degraded and stoichiometrically equivalent amounts of free fatty acids formed. The maximum rate of degradation was obtained at pH 7.0 and at 200 muM lysolecithin. With increasing amounts of gallbladder epithelial cell constituents the reaction became faster. After heating the epithelial components at 70 degrees C for 10 min the reaction was inhibited. The results suggest the presence of a heat labile lysophospholipase (phospholipase B) activity in the human gallbladder epithelium. This activity may operate to protect the gallbladder epithelium against potentially pathogenic lysolecithin activity. Its presence in the gallbladder epithelium meets the prerequisites for a local anti-inflammatory mechanism and lends further support to the hypothesis of lysolecithin as a mediator of cholecystitis.
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PMID:The biochemical prerequisites for preventing pathogenic lysolecithin activity in the human gallbladder. 99 31