{{Short description|Cell substructure in biology}} 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 [[peroxisome]]s, [[glyoxysome]]s, [[glycosome]]s and [[hydrogenosome]]s. 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== [[File:Peroxisome.svg|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 (biology and chemistry)|vesicle]] with a spherical shape, ranging from 0.2-1.5 micrometers in diameter.<ref name="smith1978">"Microbodies." Molecular Biology of Plant Cells. Ed. H. Smith. N.p.: University of California, 1978. 136-54. Print. </ref> 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 [[enzyme]]s and other proteins, but they do not seem to contain any genetic material to allow them to self-replicate.<ref name="smith1978"/>

==Function==

Microbodies contain enzymes that participate in the preparatory or intermediate stages of [[Biochemistry|biochemical reactions]] within the cell. This facilitates the breakdown of fats, alcohols and amino acids. Generally microbodies are involved in detoxification of peroxides and in photo respiration in plants. Different types of microbodies have different functions:

===Peroxisomes=== A [[peroxisome]] is a type of microbody that functions to help the body break down large molecules and detoxify hazardous substances. It contains enzymes like [[oxidase]], which can produce hydrogen peroxide as a byproduct of its enzymatic reactions. Within the peroxisome, hydrogen peroxide can then be converted to water by enzymes like [[catalase]] and [[peroxidase]]. The peroxisome was discovered and named by [[Christian de Duve]].

Peroxisomes are derived from the [[smooth endoplasmic reticulum]] under certain experimental conditions and replicate by membrane growth and division out of pre-existing organelles.<ref name="pmid16009135">{{cite journal | vauthors = Hoepfner D, Schildknegt D, Braakman I, Philippsen P, Tabak HF | title = Contribution of the endoplasmic reticulum to peroxisome formation | journal = Cell | volume = 122 | issue = 1 | pages = 85–95 | date = July 2005 | pmid = 16009135 | doi = 10.1016/j.cell.2005.04.025 | hdl = 1874/9833 | s2cid = 18837009 | hdl-access = free }}</ref><ref>{{cite journal | vauthors = Schrader M, Costello JL, Godinho LF, Azadi AS, Islinger M | title = Proliferation and fission of peroxisomes - An update | journal = Biochimica et Biophysica Acta (BBA) - Molecular Cell Research | volume = 1863 | issue = 5 | pages = 971–83 | date = May 2016 | pmid = 26409486 | doi = 10.1016/j.bbamcr.2015.09.024 | doi-access = free | hdl = 10871/18323 | hdl-access = free }}</ref><ref>{{cite journal | vauthors = Lazarow PB, Fujiki Y | title = Biogenesis of peroxisomes | journal = Annual Review of Cell Biology | volume = 1 | issue = 1 | pages = 489–530 | date = Nov 1985 | pmid = 3916321 | doi = 10.1146/annurev.cb.01.110185.002421 }}</ref> This is in line with homologies between the peroxisomal import machinery and the [[Endoplasmic Reticulum Associated Protein Degradation|ERAD]] pathway in the [[endoplasmic reticulum]],<ref name="pmid16452116">{{cite journal | vauthors = Schlüter A, Fourcade S, Ripp R, Mandel JL, Poch O, Pujol A | title = The evolutionary origin of peroxisomes: an ER-peroxisome connection | journal = Molecular Biology and Evolution | volume = 23 | issue = 4 | pages = 838–45 | date = April 2006 | pmid = 16452116 | doi = 10.1093/molbev/msj103 | doi-access = free }}</ref><ref name="pmid16556314">{{cite journal | vauthors = Gabaldón T, Snel B, van Zimmeren F, Hemrika W, Tabak H, Huynen MA | title = Origin and evolution of the peroxisomal proteome | journal = Biology Direct | volume = 1 | page = 8 | date = March 2006 | pmid = 16556314 | pmc = 1472686 | doi = 10.1186/1745-6150-1-8 | doi-access = free }}</ref> along with a number of metabolic enzymes that were likely recruited from the [[mitochondria]].<ref name="pmid16556314" />

Glyoxysomes and glycosomes are known to be peroxisome variants because they not only have similar structures, but are also built using similar processes, using related proteins, and contains related enzymes that carry out often recognizably related pathways.<ref name="Three"/> Even when radically different enzymes are involved, the [[signal peptide]]s are conserved.<ref>{{cite journal |last1=Keller |first1=GA |last2=Krisans |first2=S |last3=Gould |first3=SJ |last4=Sommer |first4=JM |last5=Wang |first5=CC |last6=Schliebs |first6=W |last7=Kunau |first7=W |last8=Brody |first8=S |last9=Subramani |first9=S |title=Evolutionary conservation of a microbody targeting signal that targets proteins to peroxisomes, glyoxysomes, and glycosomes. |journal=The Journal of cell biology |date=September 1991 |volume=114 |issue=5 |pages=893-904 |doi=10.1083/jcb.114.5.893 |pmid=1831458}}</ref>

====Glyoxysomes==== [[Glyoxysome]]s are specialized peroxisomes found in plants and [[Mold (fungus)|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 ==== [[Glycosome]]s 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.<ref name= "Three">{{cite journal | author = Parsons M | title = Glycosomes: parasites and the divergence of peroxisomal purpose | journal = Mol Microbiol | volume = 53 | issue = 3 | pages = 717–24 | year = 2004 | pmid = 15255886 | doi = 10.1111/j.1365-2958.2004.04203.x| doi-access = free }}</ref>

=== Hydrogenosome === [[Hydrogenosome]]s are a variant of [[mitochondria]] to produce molecular [[hydrogen]] and [[Adenosine triphosphate|ATP]] in anaerobic conditions.<ref name=":0">{{cite journal | vauthors = de Graaf RM, Duarte I, van Alen TA, Kuiper JW, Schotanus K, Rosenberg J, Huynen MA, Hackstein JH | display-authors = 6 | title = The hydrogenosomes of Psalteriomonas lanterna | journal = BMC Evolutionary Biology | volume = 9 | issue = 1 | article-number = 287 | date = December 2009 | pmid = 20003182 | pmc = 2796672 | doi = 10.1186/1471-2148-9-287 | doi-access = free | bibcode = 2009BMCEE...9..287D }}</ref> Their link to the mitochondria is proven by their structual and functional similarities and their use of mitochondrion-related proteins (imported from the nucleus).<ref name=":2">{{cite journal | vauthors = Rada P, Doležal P, Jedelský PL, Bursac D, Perry AJ, Šedinová M, Smíšková K, Novotný M, Beltrán NC, Hrdý I, Lithgow T, Tachezy J | display-authors = 6 | title = The core components of organelle biogenesis and membrane transport in the hydrogenosomes of Trichomonas vaginalis | journal = PLOS ONE | volume = 6 | issue = 9 | article-number = e24428 | date = 2011-09-15 | pmid = 21935410 | pmc = 3174187 | doi = 10.1371/journal.pone.0024428 | bibcode = 2011PLoSO...624428R | doi-access = free }}</ref><ref>{{cite journal | vauthors = Mai Z, Ghosh S, Frisardi M, Rosenthal B, Rogers R, Samuelson J | title = Hsp60 is targeted to a cryptic mitochondrion-derived organelle ("crypton") in the microaerophilic protozoan parasite Entamoeba histolytica | journal = Molecular and Cellular Biology | volume = 19 | issue = 3 | pages = 2198–205 | date = March 1999 | pmid = 10022906 | doi = 10.1128/MCB.19.3.2198 | pmc = 84012 | doi-access = free }}</ref> Most of them are genomeless, but two examples are known to have a genome recognizably related to mitochondrial genomes.<ref name=":3">{{cite journal | vauthors = Stechmann A, Hamblin K, Pérez-Brocal V, Gaston D, Richmond GS, van der Giezen M, Clark CG, Roger AJ | display-authors = 6 | title = Organelles in Blastocystis that blur the distinction between mitochondria and hydrogenosomes | journal = Current Biology | volume = 18 | issue = 8 | pages = 580–5 | date = April 2008 | pmid = 18403202 | pmc = 2428068 | doi = 10.1016/j.cub.2008.03.037 | bibcode = 2008CBio...18..580S }}</ref>

== History ==

Microbodies were first discovered and named in 1954 by Rhodin.<ref name="deduveandbaudhuin"> {{cite journal | author = de Duve C and Baudhuin P | title = Peroxisomes (Microbodies and Related Particles) | journal = Physiological Reviews | volume = 46 | pages = 323–357 | year = 1966 | issue = 2 | url=http://physrev.physiology.org/content/46/2/323.full.pdf |doi = 10.1152/physrev.1966.46.2.323 | pmid = 5325972 }}</ref> Two years later in 1956, Rouiller and Bernhard presented the first worldwide accepted images of microbodies in liver cells.<ref name="deduveandbaudhuin" /> Then in 1965, Christian de Duve and coworkers isolated microbodies from the liver of a rat. De Duve also believed that the name microbody was too general and chose the name of [[peroxisome]] because of its relationship with hydrogen peroxide.<ref name="pmid4389648">{{cite journal | author = de Duve C | title = The peroxisome: a new cytoplasmic organelle | journal = Proc. R. Soc. Lond. B Biol. Sci. | volume = 173 | issue = 30 | pages = 71–83 | year = 1969 | pmid = 4389648 | doi = 10.1098/rspb.1969.0039 | bibcode = 1969RSPSB.173...71D | s2cid = 86579094 }}</ref> In 1967, Breidenbach and Beevers were the first to isolate microbodies from plants, which they named [[glyoxysome]]s because they were found to contain enzymes of the [[glyoxylate cycle]].

==References== {{Reflist}}{{Portal|Biology }} [[Category:Cell biology]] [[Category:Organelles]]