A modification in the metabolic pathway of Pyrococcus furiosus has demonstrated an adaptation to being a hyperthermophile. Archaebacteria are anaerobes that utilize the reduction of sulfur as a source of energy for growth. Pyrobaculum, Pyrodictum, and Hyperthermos rely on dihydrogen or molecular hydrogen as their reducing agent.
Pyrococcus furiosus uses a fermentative type metabolism for growth versus reduction. It oxidizes carbohydrates such as dehydrogenase, carbon dioxide, and organic acids (Makund). To remove or detoxify itself of dihydrogen, an inhibitor of growth, it reduces elemental sulfur to hydrogen sulfide. Initial studies showed that a protein called tungsten-containing iron-sulfur protein (RTP) stimulated the growth of P.
furiosus. Due to previous research of the first proteins observed in this organism, RTP was expected to catalyze oxidoreductase-type reactions of very low potential as well as using ferredoxin as an electron acceptor (Makund). However this is not the case.
It was predicted that RTP had a catalytic function when compared to an enzyme, carboxylic acid reductase, a participant in a reaction of low potential and contingent on tungsten in order to carry out its enzymatic function. Carboxylic acid reductase catalyzes the reversible reduction of carboxylic acids to complementary aldehydes (Makund). Another factor that relates these enzymes is that tungsten has been observed in purified samples of carboxylic acid reductase. Based on the results of the article, RTP was identified as a catalyst of the ferredoxin-dependent oxidation of aldehydes.
They showed how RTP is an inactive form of enzyme aldehyde ferredoxin oxidoreductase (AOR) (Kengen). This enzyme converts glyceraldehyde-3-phosphate instead of glyceraldehyde. This alteration contributes to a modified Embden-Meyerhof pathway instead of the expected pyrogylcolysis that is seen in organisms that live in normal temperatures (Kengen). This shows an adaptation in the metabolic process.