A microbody (or cytosome) is a type of organelle that is found in the cells of plants, protozoa, fungi, and animals. Organelles in the microbody family include peroxisomes, glyoxysomes, glycosomes and hydrogenosomes. In vertebrates, microbodies are especially prevalent in the liver and kidney. Many membrane bound vesicles called microbodies that contain various enzymes, are present in both plant and animal cells.
Structure
thumb|Microbody structure - a [[peroxisome]]
Microbodies are different type of bodies present in the cytosol, also known as cytosomes. A microbody is usually a vesicle with a spherical shape, ranging from 0.2-1.5 micrometers in diameter. Microbodies are found in the cytoplasm of a cell, but they are only visible with the use of an electron microscope. They are surrounded by a single phospholipid bilayer membrane and they contain a matrix of intracellular material including enzymes and other proteins, but they do not seem to contain any genetic material to allow them to self-replicate. This is in line with homologies between the peroxisomal import machinery and the ERAD pathway in the endoplasmic reticulum, along with a number of metabolic enzymes that were likely recruited from the mitochondria.
Glyoxysomes
Glyoxysomes are specialized peroxisomes found in plants and mold, which help to convert stored lipids into carbohydrates so they can be used for plant growth. In glyoxysomes the fatty acids are hydrolyzed to acetyl-CoA by peroxisomal β-oxidation enzymes. Besides peroxisomal functions, glyoxysomes also possess the key enzymes of the glyoxylate cycle.
Glycosomes
Glycosomes are specialized peroxisomes found in some protists such as the Kinetoplastida. They specialize in the breakdown of carbohydrates as well as other catabolic processes like purine salvage.
Hydrogenosome
Hydrogenosomes are a variant of mitochondria to produce molecular hydrogen and ATP in anaerobic conditions. Their link to the mitochondria is proven by their structual and functional similarities and their use of mitochondrion-related proteins (imported from the nucleus). Most of them are genomeless, but two examples are known to have a genome recognizably related to mitochondrial genomes.
History
Microbodies were first discovered and named in 1954 by Rhodin. Two years later in 1956, Rouiller and Bernhard presented the first worldwide accepted images of microbodies in liver cells. In 1967, Breidenbach and Beevers were the first to isolate microbodies from plants, which they named glyoxysomes because they were found to contain enzymes of the glyoxylate cycle.