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Organelles are membrane bound structures that compartmentalize biochemical and molecular functions. With improved molecular, biochemical and microscopy tools the diversity and function of protistan organelles has increased in recent years, providing a complex panoply of structure/function relationships. This is particularly noticeable with the description of hydrogenosomes, and the diverse array of structures that followed, having hybrid hydrogenosome/mitochondria attributes. These diverse organelles have lost the major, at one time, definitive components of the mitochondrion (tricarboxylic cycle enzymes and cytochromes), however they all contain the machinery for the assembly of Fe-S clusters, which is the single unifying feature they share. The plasticity of organelles, like the mitochondrion, is therefore evident from its ability to lose its identity as an aerobic energy generating powerhouse while retaining key ancestral functions common to both aerobes and anaerobes. It is interesting to note that the apicoplast, a non-photosynthetic plastid that is present in all apicomplexan protozoa, apart from Cryptosporidium and possibly the gregarines, is also the site of Fe-S cluster assembly proteins. It turns out that in Cryptosporidium proteins involved in Fe-S cluster biosynthesis are localized in the mitochondrial remnant organelle termed the mitosome. Hence, different organisms have solved the same problem of packaging a life-requiring set of reactions in different ways, using different ancestral organelles, discarding what is not needed and keeping what is essential. Don't judge an organelle by its cover, more by the things it does, and always be prepared for surprises., (Copyright © 2024. Published by Elsevier Inc.)

Abstract: The arginine dihydrolase (ADH) pathway has an analogous function to the urea cycle in mitochondria-containing cells, by removing nitrogen from amino acids and generating ATP. Subcellular localization of the ADH pathway enzymes in Trichomonas vaginalis revealed that arginine deiminase (ADI) localizes to the hydrogenosome, a mitochondrion-like organelle of anaerobic protists. However the other enzymes of the ADH pathway, ornithine carbamyltransferase and carbamate kinase localize to the cytosol. Three gene sequences of T. vaginalis ADI (ADI 1–3) were identified in the T. vaginalis genome, all having putative mitochondrial targeting sequences. The ADI sequences were cloned and used to probe T. vaginalis using a carboxyterminal di-hemogglutinin epitope tag which demonstrated co-localization with malic enzyme confirming the hydrogenosome localization of this enzyme. [ABSTRACT FROM AUTHOR]

The article discusses the result of the study concerning biochemical characterization of a mitochondrial-like organelle (MLO) from blastocystis. It has been reported that a MLO was insulated from isotonic homogenates of blastocystis. It is the biochemical characterization altered the presentation of several key enzymes that permitted the creation of a metabolic pathway comprising of an incomplete Krebs cycle connected to the oxygen-sensitive enzymes pyruvate. The result revealed that blastocystis organelle is important in biochemical differences from traditional mitochondria and hydrogenosomes. In addition, the study suggest based on the result that the blastocystis organelle belongs into the category of a MLO.