The process of organohalide respiration, uses reductive dehalogenation to produce energy that can be used by the respiring microorganism to carry out its growth and metabolism. Halogenated organic compounds are used as the terminal electron acceptor, which results in their dehalogenation. Reductive dehalogenation is the process by which this occurs. It involves the reduction of halogenated compounds by removing the halogen substituents, while simultaneously adding electrons to the compound. Hydrogenolysis and vicinal reduction are the two known processes of this mechanism that have been identified. In both processes, the removed halogen substituents are released as anions.  Reductive dehalogenation is catalyzed by reductive dehalogenases, which are membrane-associated enzymes. A number of not only membrane-associated but also cytoplasmic hydrogenases, in some cases as part of the protein complexes, are predicted to play roles in the organohalide respiration process. Most of these enzymes contain iron-sulfur (Fe-S) clusters, and a corrinoid cofactor at their active sites. Although the exact mechanism is unknown, research suggests that these two components of the enzyme may be involved in the reduction.