What is microsomal protein?
Microsomes are artificial structures derived from pieces of endoplasmic reticulum (ER) formed during tissue homogenization. They are prepared by differential centrifugation at 10,000 and 100,000 × g and contain cytochrome P450 enzymes (CYPs), but do not contain soluble enzymes.
What are microsomal enzymes?
Microsomal enzymes are typically found in the endoplasmic reticulum of hepatocytes. Microsomes are fragments of endoplasmic reticulum and attached ribosomes that are isolated together when homogenized cells are centrifuged.
What is the meaning of Microsome?
1 : any of various minute cellular structures. 2 : a particle in a particulate fraction that is obtained by heavy centrifugation of broken cells and consists of various amounts of ribosomes, fragmented endoplasmic reticulum, and mitochondrial cristae.
What is microsomal fraction?
a collection of tiny subcellular particles, invisible with the light MICROSCOPE, that are produced during DIFFERENTIAL CENTRIFUGATION of eukaryotic cells. The microsomal fraction is thus an artefact produced by the preparation process, rather than a biological entity. …
What are liver microsomes?
Liver microsomes are subcellular fractions which contain membrane bound drug metabolizing enzymes. Microsomes can be used to determine the in vitro intrinsic clearance of a compound. The use of species-specific microsomes can be used to enable an understanding of interspecies differences in drug metabolism.
What is the MEOS pathway?
The microsomal ethanol oxidizing system (MEOS) is an alternate pathway of ethanol metabolism that occurs in the smooth endoplasmic reticulum in the oxidation of ethanol to acetaldehyde.
What is the role of microsomal enzyme?
Inducers of microsomal enzymes stimulate the metabolism or synthesis of several normal body substrates such as steroid hormones, pyridine nucleotides, cytochromes, and bilirubin. Recent studies suggest that inducers of liver microsomal enzymes enhance the hydroxylation of steroids in man.
What is microsomal assay?
The microsomal stability assay is primarily used to investigate Phase I metabolism using NADPH as the enzyme co-factor. However liver microsomes can also be used to study Phase II metabolism if the correct incubation conditions are used.
What triggers MEOS pathway?
While playing only a minor role in ethanol metabolism in average individuals, MEOS activity increases after chronic alcohol consumption. The MEOS pathway requires the CYP2E1 enzyme, part of the cytochrome P450 family of enzymes, to convert ethanol to acetaldehyde.
How are proteins removed from the microsomal membrane?
Washing is an important step to remove proteins and CLDs peripherally associated with the microsomal membrane. Microsomal membranes are pelleted by ultracentrifugation at 106,000 × g for 1 h, while peripheral proteins (cytosolic side) remain in the supernatant.
How long to incubate microsomal protein for stability?
For microsomal stability determination, the compound is typically incubated in approximately 1.0 mg/ml microsomal protein, phosphate buffer, pH 7.4 at 37°C for 30 minutes.
How are microsomal membranes pelleted for 1 h?
Microsomal membranes are pelleted by ultracentrifugation at 106,000 × g for 1 h, while peripheral proteins (cytosolic side) remain in the supernatant. Jim Vrbanac, Richard Slauter, in A Comprehensive Guide to Toxicology in Preclinical Drug Development, 2013
How are microsomes used in in vitro drug metabolism studies?
Microsomes containing specific individual human CYPs and UGTs have become extremely important methodological options for in vitro drug metabolism studies, in particular to investigate the contribution of enzymes involved in the biotransformation of an NCE.2,26
