WordNet

of or relating to microsomes
a tiny granule in the cytoplasm that is where protein synthesis takes place under the direction of mRNA

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/01/26 18:17:59」(JST)

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In cell biology, microsomes are vesicle-like artifacts re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; by definition, microsomes are not ordinarily present in living cells.^[1]

Microsomes can be concentrated and separated from other cellular debris by differential centrifugation. Unbroken cells, nuclei, and mitochondria sediment out at 10,000g, whereas soluble enzymes and fragmented ER, which contains cytochrome P450 (CYP), remain in solution (g is the Earth's gravitational acceleration). At 100,000g, achieved by faster centrifuge rotation, ER sediments out of solution as a pellet but the soluble enzymes remain in the supernatant. In this way, cytochrome P450 in microsomes is concentrated and isolated. Microsomes have a reddish brown color, due to the presence of the iron-containing co-factor, heme (haem), in the P450s. P450s are highly abundant in livers of rats, mice and humans.

Microsomes are a valuable tool for investigating the metabolism of compounds (enzyme inhibition, clearance and metabolite identification) and for examining drug-drug interactions by in vitro-research. Researchers often select microsome lots based on the enzyme activity level of specific CYPs. Some lots are available to study specific populations (example: lung microsomes from smokers or non-smokers) or divided into classifications to meet target CYP activity levels for inhibition and metabolism studies.

Researchers use microsomes to mimic the activity of the endoplasmic reticulum in a test tube and conduct experiments that require protein synthesis on a membrane; they provide a way for scientists to figure out how proteins are being made on the ER in a cell by reconstituting the process in a test tube.

References

^ Voet, Donald; Voet, Judith G. (2004). Biochemistry (3rd ed.). Wiley. p. 1309. ISBN 0-471-19350-X.

External links

MeSH A11.284.835.540
The use of microsomes to measure clearance The performance of in vitro microsomal clearance studies including analysis of the data.

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Improved integrity of liver microsomal fraction https://www.researchgate.net/publication/233425223_Studies_on_liver_microsomal_fraction?ev=prf_pub

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English Journal

Phosphatidylserine-containing liposomes: potential pharmacological interventions against inflammatory and immune diseases through the production of prostaglandin e(2) after uptake by myeloid derived phagocytes.

Wu Z, Nakanishi H.SourceDepartment of Aging Science and Pharmacology, Faculty of Dental Science, Kyushu University, Fukuoka, 812-8582, Japan, zhouw@dent.kyushu-u.ac.jp.
Archivum immunologiae et therapiae experimentalis.2011 Jun;59(3):195-201. Epub 2011 Apr 10.
Phosphatidylserine (PS), which is normally located on the inner leaflet of the plasma membrane, translocates to the outer leaflet at the early stage of apoptosis. The PS externalization provides a signal for phagocytes to initiate uptake of apoptotic cells. After phagocytosis of apoptotic cells, pha
PMID 21479802

A glycosyltransferase-enriched reconstituted membrane system for the synthesis of branched O-linked glycans in vitro.

Susini S, Jeanneau C, Mathieu S, Carmona S, El-Battari A.AbstractMimicking the biochemical reactions that take place in cell organelles is becoming one of the most important challenges in biological chemistry. In particular, reproducing the Golgi glycosylation system in vitro would allow the synthesis of bioactive glycan polymers and glycoconjugates for many future applications including treatments of numerous pathologies. In the present study, we reconstituted a membrane system enriched in glycosyltransferases obtained by combining the properties of the wheat germ lectin with the dialysable detergent n-octylglucoside. When applied to cells engineered to express the O-glycan branching enzyme core2 beta (1,6)-N-acetylglucosaminyltransferase (C2GnT-I), this combination led to the reconstitution of lipid vesicles exhibiting an enzyme activity 11 times higher than that found in microsomal membranes. The enzyme also showed a slightly higher affinity than its soluble counterpart toward the acceptor substrate. Moreover, the use of either the detergent re-solubilization, glycoprotein substrates or N-glycanase digestion suggests that most of the reconstituted glycosyltransferases have their catalytic domains in an extravesicular orientation. Using the disaccharide substrate Galβ1-3GalNAc-O-p-nitrophenyl as a primer, we performed sequential glycosylation reactions and compared the recovered oligosaccharides to those synthesized by cultured parental cells. After three successive glycosylation reactions using a single batch of the reconstituted vesicles and without changing the buffer, the acceptor was transformed into an O-glycan with chromatographic properties similar to glycans produced by C2GnT-I-expressing cells. Therefore, this new and efficient approach would greatly improve the synthesis of bioactive carbohydrates and glycoconjugates in vitro and could be easily adapted for the study of other reactions naturally occurring in the Golgi apparatus such as N-glycosylation or sulfation.
Biochimica et biophysica acta.2011 Jun;1808(6):1509-19. Epub 2010 Nov 18.
Mimicking the biochemical reactions that take place in cell organelles is becoming one of the most important challenges in biological chemistry. In particular, reproducing the Golgi glycosylation system in vitro would allow the synthesis of bioactive glycan polymers and glycoconjugates for many futu
PMID 21081110

Japanese Journal

Liver microsomal triglyceride transfer protein activator may be a possible therapeutic agent in non-alcoholic steatohepatitis (Forum minireview: Novel findings for the development of drug therapy for various liver diseases)

Fujita Koji,Imajo Kento,Shinohara Yoshiyasu [他]
Journal of pharmacological sciences 115(3), 270-273, 2011-03
NAID 40018724632

Protein disulfide isomerase knockdown-induced cell death is cell-line-dependent and involves apoptosis in MCF-7 cells

Hashida Tomoyo,Kotake Yaichiro,Ohta Shigeru
The Journal of Toxicological Sciences 36(1), 1-7, 2011
… Protein disulfide isomerase (PDI) is a multifunctional protein that catalyzes disulfide bond formation and assists protein folding, as well as being a structural subunit of microsomal triglyceride transfer protein (MTP) and prolyl 4-hydroxylase (P4HD), and an estrogen and thyroid hormone-binding protein. …
NAID 130000438633

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