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The <hydrogenosomes> and <mitosomes> are specialized mitochondrion-related <organelles> found in various anaerobic or oxygen-limited <eukaryotes>. \b[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.<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]{ref}
\b[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.<Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation by Jorge Tovar and others>[Abstract: localization and iron-sulfur protein maturation]{ref} Their functions are lineage-dependent: <Entamoeba histolytica> <mitosomes> compartmentalize a <sulfate activation> pathway.<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]{ref} Thus neither organelle class should be described simply as a nonfunctional <mitochondrion>.
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