A mitosome (also called a crypton in early literature)[1] is a mitochondrion-related organelle (MRO)[2] found in a variety of parasitic unicellular eukaryotes, such as members of the supergroup Excavata.
[7] The mitosome has been detected only in anaerobic or microaerophilic eukaryotes which do not have fully developed mitochondria, and hence do not have the capability of gaining energy from mitochondrial oxidative phosphorylation.
[9] Current knowledge indicates mitosomes probably play a role in Fe–S cluster assembly, since they do not display any of the proteins involved in other major mitochondrial functions (aerobic respiration via oxidative phosphorylation, haem biosynthesis) while they do display proteins required for Fe–S cluster biosynthesis (like frataxin, cysteine desulfurase, Isu1 and a mitochondrial Hsp70).
[2][6][9] Additionally, modified mitosomes in the intracellular parasitic protist Paramikrocytos canceri may biosynthesize phospholipids and support glycolytic ATP production, based on genomic and transcriptomic analysis.
[8] It has been proposed that MROs such as mitosomes evolved in anoxic marine environments which predominated during the Proterozoic, thus explaining their anaerobic metabolic functionality.