Chlorite dismutase

Chlorite dismutase (Cld) is an enzyme that plays a crucial role in the detoxification of chlorite, an oxyanion of chlorine. This enzyme is particularly significant in microorganisms that utilize chlorate or perchlorate as terminal electron acceptors in their respiratory processes. Chlorite dismutase catalyzes the conversion of chlorite into chloride and dioxygen, a reaction that is essential for the metabolism of these organisms and for the bioremediation of environments contaminated with chlorate or perchlorate.

Function

The primary function of chlorite dismutase is to detoxify chlorite, which is toxic to cells, by converting it into less harmful substances. The enzyme catalyzes the reaction:

2 ClO2- + 2 H+ → Cl- + O2 + H2O

This reaction is vital for organisms that reduce chlorate (ClO3-) or perchlorate (ClO4-) to chlorite (ClO2-) during their respiratory process. Without the action of chlorite dismutase, the accumulation of chlorite would be detrimental to the cell.

Structure

Chlorite dismutase is a heme protein, meaning it contains a heme group as a prosthetic part of its structure. The heme group is essential for the enzyme's catalytic activity. The enzyme exists in various oligomeric forms, with the pentamer being the most common. Each monomer of the enzyme consists of a heme domain that binds the chlorite substrate.

Genetics

The gene encoding chlorite dismutase, cld, has been identified in several microorganisms capable of chlorate and perchlorate reduction. The regulation of this gene is closely linked to the presence of chlorate or perchlorate in the environment, indicating that its expression is induced by these compounds.

Biotechnological Applications

Due to its ability to neutralize chlorite, chlorite dismutase has potential applications in bioremediation. It can be used in the treatment of industrial effluents and drinking water contaminated with chlorate or perchlorate. Furthermore, the enzyme's ability to produce dioxygen from chlorite presents opportunities for bioenergy applications, such as in biofuel cells.

Environmental Significance

The activity of chlorite dismutase is crucial for the microbial reduction of chlorate and perchlorate, which are environmental pollutants. These compounds are often found in contaminated sites due to their use in industrial processes. Microorganisms equipped with chlorite dismutase can thus contribute to the detoxification of such environments.

See Also

• Enzyme
• Heme protein
• Bioremediation
• Oxyanion
• Microorganism