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Abstract: An enzymic lipid peroxidation system has been demonstrated in the microsomal fraction of rat brain and the requirements and optimal conditions for assay determined. The involvement of NADPH-cytochrome c reductase was demonstrated in vesicles reconstituted with lipids extracted from the brain microsomal fraction. Further characterization of the system made use of substances shown to inhibit the liver microsomal system. α-Tocopherol was shown to be an effective inhibitor of lipid peroxidation in the brain microsomal system, whereas Na2SO3 had no effect, which is indicative that free radical transfer occurs only in the hydrophobic regions. Neither superoxide dismutase nor catalase inhibited lipid peroxidation. The implications of an NADPH-cytochrome c reductase-dependent lipid peroxidation system that is not linked to a drug hydroxylation system and appears to differ from the liver microsomal system in a number of other ways are discussed.  相似文献   

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Purification of hepatic microsomal membranes   总被引:5,自引:0,他引:5  
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Housefly UDP-glucosyltransferase activity towards p-nitrophenol was demonstrated in a system in vitro. The activity is localized in the microsomal fraction, requires UDP-glucose, is slightly stimulated by Mg2+ and is activated optimally over a wide range of detergent concentration. Phenobarbital increases the enzyme(s) activity about 3-fold, with p-nitrophenol as substrate, which differs from the corresponding mammalian glucuronyltransferase.  相似文献   

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Selenium and hepatic microsomal hemoproteins   总被引:3,自引:0,他引:3  
The microsomal share of liver homogenate 75Se after injection of a tracer dose of 75SeO32? was three times greater in rats fed a selenium-deficient diet than in rats fed a selenium-adequate diet. Basal levels of microsomal cytochromes P-450 and b5 were unaffected by selenium deficiency. However, induction of these cytochromes by phenobarbital was markedly inpaired in selenium-deficient rats, whereas liver weight increase and NADPH cytochrome c reductase induction were not impaired. These data indicate that selenium is essential for phenobarbital induction of microsomal hemoproteins.  相似文献   

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It was recently reported by Yamada et al. (Yamada N., Murase T., Akanuma Y., Ikakura H. and Kosaka K. (1979) Biochim. Biophys. Acta 575, 128–134) that the guinea-pig has no hepatic heparin-releasable lipase. We have, however, found a low but definite lipase activity in guinea-pig post-heparin plasma with the characteristics of the hepatic lipase. This activity, as measured in our assay, is only about one-tenth of that in rat post-heparin in plasma. Although the activity is thus much lower than.in some other animals, its presence demonstrates that the guinea-pig is not qualitatively but only quantitatively different in this respect.  相似文献   

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When the microsomal fraction of Saccharomyces cerevisiae was incubated with farnesyl pyrophosphate or presqualene pyrophosphate in the presence of Mn2+, dehydrosqualene was formed. Incubation of the reaction mixture in the presence of NADPH gave squalene, not dehydrosqualene, as the product. Little dehydrosqualene was formed when Mn2+ was replaced with Mg2+. These observations suggest that dehydrosqualene formation is closely associated with squalene synthesis in yeast, which synthesizes neither carotenes nor related pigments.  相似文献   

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The specificity of the L-serine base-exchange enzyme towards the fatty acid composition of the phospholipid substrate was investigated with a rat liver microsomal fraction. The relative rates of L-serine incorporation into saturated-hexaenoic, saturated-pentaenoic, saturated-tetraenoic, saturated-trienoic, dienoic-dienoic, monoenoic-dienoic, saturated-dienoic and saturated-monoenoic + saturated-saturated phosphatidylserine molecular species were 42, 5, 23, 4, 5, 4, 5 and 11% respectively. This is similar to, but not identical with, the relative mass abundance of these molecular species in total liver cell phosphatidylserines. The results indicate that the substrate-specificity of the L-serine base-exchange enzyme can at least in part explain the observed fatty acid composition of rat liver phosphatidylserines.  相似文献   

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Studies were performed on methods of storage of rat jejunal tissue that would preserve activities of the lipid reesterifying enzymes, acyl CoA:monoglyceride acyltransferase and fatty acid CoA ligase. Storage at -80 degrees C of microsomes prepared from jejunal mucosa or storage of lyophilized microsomes at -20 degrees C was shown to preserve acyl CoA:monoglyceride acyltransferase very well for a matter of weeks. Preservation of fatty acid CoA ligase activity was adequate with either method, but results were not as good as for the transacylase enzyme.  相似文献   

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