Studies on the physiological function and biochemical properties of the frhAGB-encoding hydrogenase from a non-methanogenic hyperthermophilic archaeon

Abstract

The F420-reducing hydrogenase has been known as a key enzyme in methanogenesis. Its homologs identified in non-methanogenic hyperthermophilic archaea were distinguished from those of most methanogens with respect to the phylogenetic analysis of the α and β subunits, organization of frhAGB genes, and conservation of F420-coordinating residues in the β subunits. The trimeric enzyme complex was purified from T. onnurineus NA1 and exhibited catalytic activity toward the electron acceptors such as viologens and flavins but not the deazaflavin coenzyme F420. The phenotypic changes associated with deletion and overexpression of frhAGB genes were investigated in T. onnurineus NA1. The deletion and overexpression of those genes enhanced growth on the CO- and formate-containing media, respectively. Transcriptional and translational levels of several hydrogenase genes were affected by frhAGB deletion, leading to the change in H2 productivity. The correlation between frhAGB-encoding hydrogenase and other hydrogenases will be discussed.s of the α and β subunits, organization of frhAGB genes, and conservation of F420-coordinating residues in the β subunits. The trimeric enzyme complex was purified from T. onnurineus NA1 and exhibited catalytic activity toward the electron acceptors such as viologens and flavins but not the deazaflavin coenzyme F420. The phenotypic changes associated with deletion and overexpression of frhAGB genes were investigated in T. onnurineus NA1. The deletion and overexpression of those genes enhanced growth on the CO- and formate-containing media, respectively. Transcriptional and translational levels of several hydrogenase genes were affected by frhAGB deletion, leading to the change in H2 productivity. The correlation between frhAGB-encoding hydrogenase and other hydrogenases will be discussed.