sodC

SodC is the gene that encodes the periplasmic copper–zinc superoxide dismutase (CuZnSOD) in many Gram-negative bacteria. It is part of the sod gene family, which also includes sodA (manganese SOD) and sodB (iron SOD) that function in the cytoplasm. The sodC-encoded enzyme is exported to the periplasm via a signal peptide at the N-terminus, and the mature enzyme resides in the periplasm where it encounters reactive oxygen species.

Function and mechanism: SodC catalyzes the dismutation of superoxide radicals (O2−) into hydrogen peroxide (H2O2) and molecular oxygen (O2). Its active site contains copper and zinc, with copper cycling between oxidation states during catalysis and zinc helping to stabilize the structure. In the periplasmic space of Gram-negative bacteria, SodC helps detoxify superoxide generated by aerobic metabolism and by host immune cells, contributing to oxidative stress resistance.

Biological and clinical relevance: In many pathogenic species, SodC enhances survival during infection by defending against the oxidative burst from macrophages and neutrophils. Expression of sodC is commonly linked to oxidative stress responses and may be regulated by regulators such as OxyR or SoxRS, depending on the species. Some bacteria possess multiple sodC alleles (for example sodC1 and sodC2) with differing export efficiencies or expression patterns, reflecting adaptation to environmental or immune challenges.

Genetic diversity and structure: The sodC gene typically encodes a periplasmic CuZnSOD that is exported via the Sec pathway. In contrast to the cytoplasmic sodA and sodB, sodC products are localized to the periplasm and may function as dimers or rely on periplasmic disulfide formation for stability.

See also: sodA, sodB, superoxide dismutase, oxidative stress response.