The Wolfe Cycle is a methanogenic pathway used by archaea; the archaeon takes H2 and CO2 and cycles them through a various intermediates to create methane. [1] The Wolfe Cycle is modified in different orders and classes of archaea as per the resource availability and requirements for each species, but it retains the same basic pathway. [1] The pathway begins with the reducing carbon dioxide to formylmethanofuran. [1] The last step uses heterodisulfide reductase (Hdr) to reduce heterodisulfide into Coenzyme B and Coenzyme M using Fe4S4 clusters. [1] [2] Evidence suggests this last step goes hand-in-hand with the first step, and feeds back into it, creating a cycle. [1] At various points in the Wolfe Cycle, intermediates that are formed are taken out of the cycle to be used in other metabolic processes. [1] [3] Since intermediates are being taken out at various points in the cycle, there is also a replenishing (anaplerotic) reaction that feeds into the Wolfe cycle, this is to regenerate necessary intermediates for the cycle to continue. [1] Overall, including the replenishing reaction, the Wolfe Cycle has a total of nine steps. [1] While Obligate reducing methanogens perform additional steps to reduce CO2 to .
