Function of coenzyme F 420 -dependent NADP reductase in methanogenic archaea containing an NADP-dependent alcohol dehydrogenase

Abstract

Methanogenic archaea growing on ethanol or isopropanol as the electron donor for CO2 reduction to CH4 contain either an NADP-dependent or a coenzyme F420-dependent alcohol dehydrogenase. We report here that in both groups of methanogens, the N5, N10-methylenetetrahydromethanopterin dehydrogenase and the N5, N10-methylenetetrahydromethanopterin reductase, two enzymes involved in CO2 reduction to CH4, are specific for F420. This raised the question how F420H2 is regenerated in the methanogens with an NADP-dependent alcohol dehydrogenase. We found that these organisms contain catabolic activities of an enzyme catalyzing the reduction of F420 with NADPH. The F420-dependent NADP reductase from Methanogenium organophilum was purified and characterized. The N-terminal amino acid sequence showed 42% sequence identity to a putative gene product in Methanococcus jannaschii, the total genome of which has recently been sequenced.

npd gene functions of Rhodococcus (opacus) erythropolis HL PM-1 in the initial steps of 2,4,6-trinitrophenol degradation b bThe GenBank accession number for the sequence reported in this paper is AF435009.

“…Enzymes playing a role in general metabolism, with F %#! being involved, are known in mycobacteria, streptomycetes and Archaea (Berk & Thauer, 1997 ;Eker et al, 1989 ;Purwantini & Daniels, 1996). For this reason, even though specific for F %#!…”

Physiology, Biochemistry, and Applications of F420- and Fo-Dependent Redox Reactions

“…However, F 420 is not involved in the aceticlastic pathway, which depends on a largely distinct set of enzymes (175, 181). In addition to mediating methanogenesis, dedicated F 420 -dependent enzymes mediate a wide array of other cellular reactions in methanogens, including reduction of NADP for biosynthetic pathways (Fno) (22), mobilization of sulfite as a sulfur source (Fsr) (51,191), and detoxification of atmospheric O 2 (Fpr) (161,192). Methanogens with cytochromes can use F 420 H 2 generated through the methylotrophic pathway as an input to the respiratory chain using the proton-translocating F 420 H 2 -reducing methanophenazine reductase (Fpo) (162,193).…”

“…Whereas methanogens oxidize primary alcohols (e.g., ethanol) using standard NADP-reducing alcohol dehydrogenases (Adh) (22,270), some can also metabolize secondary and cyclic alcohols using a phylogenetically unrelated class of F 420 -dependent secondary alcohol dehydrogenases (Adf) (271,272). The enzymes that mediate this are sparsely distributed, encoded by genes on just six sequenced methanogens in the NCBI database, all of the class Methanomicrobia.…”

“…Later, it was realized that F 420 is also synthesized by sulfate-reducing archaea (19), halophilic archaea (20), and likely methanotrophic archaea (21). As a result of more than 5 decades of study, scientists developed a rich understanding of the physiology and biochemistry of F 420 in the methanogenic and sulfate-reducing archaea (22), as summarized in section 3.…”

Aplicação conjunta de tratamento anaeróbio termofílico por lodo granular e de mediadores redox na remoção de cor de águas residuárias têxteis

“…Porém, muito provavelmente deve ser relacionada com a competição entre metanogênese e a redução dos corantes, pelos equivalentes reduzidos gerados na conversão do doador de elétrons. Por exemplo na metanogênese a partir do acetato, as enzimas envolvidas não utilizam NAD + ou NADP + como coenzimas, e sim uma coenzima do tipo 5-dezaflavin F 420 (Berk e Thauer, 1997). É presentemente aceito que NADH ou NAD(P)H são os doadores de elétrons primários na redução biológica de corantes azo (Stolz, 2001;Blumel e Stolz, 2003).…”