In-gel SOD assay reveals SOD-2 is the single active, water-soluble SOD enzyme in C.

The nematode C. elegans has a contingent of five sod genes, one of the largest among aerobic organism. Earlier studies revealed each of the five sod genes is capable of making perfectly active SOD proteins in heterologous expressions systems therefore none appears to be a pseudogene. Yet deletion of the entire contingent of sod genes fails to impose any effect on the survival of C. elegans except these animals appear more sensitive to extraneously applied oxidative stress condition. We asked how many of the five sod genes are actually active in C. elegans through an in-gel SOD activity analysis. Here we provide evidence that out of the five genes only the mitochondrial SOD gene is active in C. elegans, albeit at a much lesser amount compared to D. melanogaster and E. coli. Mutant analysis further confirmed that among the mitochondrial forms, SOD-2 is the only naturally active SOD in C. elegans.