Microsome
Encyclopedia
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.
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.
Cell biology
Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...
, microsomes are vesicle-like
Vesicle (biology)
A vesicle is a bubble of liquid within another liquid, a supramolecular assembly made up of many different molecules. More technically, a vesicle is a small membrane-enclosed sack that can store or transport substances. Vesicles can form naturally because of the properties of lipid membranes , or...
artifacts re-formed from pieces of the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
(ER) when eukaryotic cells are broken-up in the laboratory; by definition, microsomes are not ordinarily present in living cells.
Microsomes can be concentrated and separated from other cellular debris by differential centrifugation
Differential centrifugation
Differential centrifugation is a common procedure in microbiology and cytology used to separate certain organelles from whole cells for further analysis of specific parts of cells. In the process, a tissue sample is first homogenised to break the cell membranes and mix up the cell contents...
. Unbroken cells, nuclei
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
, 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
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
identification) and for examining drug-drug interactions by in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
-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.