Proposed pathway for the metabolism of aldehydes produced during glucose and amino acid fermentation in heterotrophic hyperthermophilic archaea. POR, IOR, VOR, and KGOR represent oxidoreductases that use pyruvate, indolepyruvate, 2-keto isovalerate, and 2-ketoglutarate, respectively. Fdox and Fdred, oxidized and reduced Fd, respectively; ACS, acyl-CoA synthetase.