sulfide:quinone oxidoreductase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: H2S (hydrogen sulfide) + a quinone = S0 (sulfane sulfur) + a hydroquinone. [RHEA:30239]

Sulfide:quinone oxidoreductase activity is a crucial enzymatic process involved in the oxidation of sulfide ions (S2-) to elemental sulfur (S) or sulfate (SO42-), utilizing quinones as electron acceptors. This activity is primarily associated with a specific class of enzymes called sulfide:quinone oxidoreductases, also known as SQRs. These enzymes play a critical role in the sulfur cycle, a fundamental biochemical pathway that regulates the balance of sulfur compounds in various ecosystems.

The catalytic mechanism of sulfide:quinone oxidoreductase activity involves the transfer of electrons from sulfide ions to a quinone molecule. This process is facilitated by the enzyme's active site, which typically contains iron-sulfur clusters and a heme group. The iron-sulfur clusters act as electron carriers, while the heme group serves as a binding site for sulfide.

During the reaction, sulfide binds to the heme group, where it undergoes oxidation. This oxidation process involves the removal of two electrons from sulfide, resulting in the formation of elemental sulfur or sulfate, depending on the specific enzyme and environmental conditions. The electrons released from sulfide are then transferred to the quinone molecule, which is reduced to a hydroquinone.

The reduced quinone molecule can subsequently participate in other metabolic processes, such as electron transport chains, providing energy for cellular functions.

Sulfide:quinone oxidoreductase activity is essential for various organisms, including bacteria, archaea, and eukaryotes. In bacteria, SQRs are involved in anaerobic respiration, utilizing sulfide as an electron donor to generate energy. In archaea, SQRs are implicated in sulfur metabolism, facilitating the conversion of sulfide to sulfur or sulfate. In eukaryotes, SQRs are primarily found in mitochondria, where they play a role in the detoxification of sulfide and the production of energy.

The regulation of sulfide:quinone oxidoreductase activity is influenced by various factors, including the availability of sulfide, the presence of quinones, and the cellular redox state. The activity of these enzymes can be modulated by environmental conditions, such as oxygen concentration, pH, and temperature.

In summary, sulfide:quinone oxidoreductase activity is a critical enzymatic process responsible for the oxidation of sulfide ions to elemental sulfur or sulfate, utilizing quinones as electron acceptors. This activity is fundamental to the sulfur cycle, plays a vital role in various metabolic pathways, and is essential for the survival of diverse organisms.'
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Proteins (1)

Compounds (1)