A Radical Way To Respire Using Sulfur

Naturally occurring compounds that contain sulfur not only have antioxidant properties, but also participate in respiration, according to research by an international team of scientists.

AsianScientist (Nov. 8, 2017) – An international team of scientists have discovered that sulfur-containing compounds, known for their antioxidant properties in biological systems, are also involved in respiration. They published their findings in Nature Communications.

Sulfur-containing compounds such as cysteine hydropersulfide (CysSSH) and other persulfides, are widely present in the cells of most organisms, from single-celled organisms to humans, and are found even in the natural environment and in foodstuffs. They are believed to act as antioxidants that protect cells from harmful free radicals, which are byproducts of normal cell activity or pollutants that can cause various diseases such as cancer.

However, how these reactive sulfur molecules are formed, or their precise role in these cells, is poorly understood.

In this study, a team of researchers from Tohoku University, working with colleagues in Japan, Hungary, the United Kingdom and the United States, homed in on one pathway for the formation of CysSSH inside cells. They identified the amino acid L-cysteine as a starting building block for the synthesis of CysSSH, through a reaction catalyzed by cysteinyl-tRNA synthetases (CARSs), a family of enzymes present in most mammalian cells.

There are two different types of CARS enzymes: one is present in the cytoplasm of cells and the other is located within mitochondria, which is often called the powerhouse of the cells. The researchers inactivated genes that produce the enzyme variants in both mice and humans. They found that the enzyme within the mitochondria is responsible for producing the majority of CysSSH and other persulfides.

Within the mitochondria, the enzyme is responsible for producing energy and maintaining mitochondria. Some of it also leaches into the cytoplasm where it catalyzes the reaction that produces CysSSH.

By identifying the dual roles that CARSs play, the researchers revealed their importance in antioxidant defense and energy production. This pathway supports sulfur respiration without the need for oxygen, and could pave the way for research on how enzymes could treat diseases resulting from an increase in oxidants, or through mitochondria dysfunction.


The article can be found at: Akaike et al. (2017) Cysteinyl-tRNA Synthetase Governs Cysteine Polysulfidation and Mitochondrial Bioenergetics.

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Source: Tohoku University; Photo: James St. John/Flickr/CC.
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