of human cells; consequently, these enzymes have become the targets of research for various environmental and medical reasons. Competitive inhibitors for the APS reductase in Mycobacterium tuberculosis have been studied as a new possible route for TB treatment, especially against drug-resistant and latent TB. Such inhibitors have also been studied in the context of obtaining oil and gas from reservoirs in order to better control the souring of such products. Some APS reductases have also been investigated for their role in selenium metabolism and reduction due to the chemical similarity between sulfur and selenium. APR2, the dominant APS reductase isozyme in the model plant Arabidopsis thaliana, has been implicated in the involvement of selenate tolerance and selenite metabolism. Such research may then aid in the goal of enhancing selenium phytoremediation in plants and, as a result, dietary biofortification. References Further reading EC 1.8.99 Flavoproteins Iron enzymes Enzymes of known structure Sulfur metabolism