Hydrogenosome 2026-10-20
A mitochondrion-related organelle class associated with anaerobic metabolism and, in typical examples, hydrogen and ATP production. Substrate-level phosphorylation can supply energy without a conventional oxygen-terminated respiratory chain.[ref]
The hydrogenosomes and mitosomes are specialized mitochondrion-related organelles found in various anaerobic or oxygen-limited eukaryotes. Typical hydrogenosomes support anaerobic ATP production, converting substrates such as pyruvate into products including acetate, carbon dioxide and molecular hydrogen. Substrate-level phosphorylation supplies ATP, while hydrogenase disposes of reducing equivalents as hydrogen; oxygen is not the terminal acceptor of a conventional respiratory chain in this pathway.[ref]
Hydrogenosome, a cytoplasmic organelle of the anaerobic flagellate Tritrichomonas foetus, and its role in pyruvate metabolism by Donald G. Lindmark and Miklós Müller. Abstract and biochemical characterization of hydrogenosomal pyruvate metabolism
The mitosomes retain selected essential metabolic functions but do not generate ATP by oxidative phosphorylation. In Giardia, their role includes iron-sulfur cluster assembly and protein maturation, demonstrated using organelle markers and biochemical reconstitution.[ref]
Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation by Jorge Tovar and others. Abstract: localization and iron-sulfur protein maturation
Their functions are lineage-dependent: Entamoeba histolytica mitosomes compartmentalize a sulfate activation pathway.[ref]Mitosomes in Entamoeba histolytica contain a sulfate activation pathway by Fumika Mi-ichi and others. Abstract and Results: mitosome fractionation, protein localization and activated sulfate products
Thus neither organelle class should be described simply as a nonfunctional mitochondrion.