Pyruvate metabolism of the hyperthermophilic archaebacterium Pyrococcus furiosus

Abstract

The hyperthermophilic anaerobe Pyrococcus furiosus was found to grow on pyruvate as energy and carbon source. Growth was dependent on yeast extract (0.1%). The organism grew with doublings times of about 1 h up to cell densities of 1–2×108 cells/ml. During growth 0.6–0.8 mol acetate and 1.2–1.5 mol CO2 and 0.8 mol H2 were formed per mol of pyruvate consumed. The molar growth yield was 10–11 g cells(dry weight)/mol pyruvate. Cell suspensions catalyzed the conversion of 1 mol of pyruvate to 0.6–0.8 mol acetate, 1.2–1.5 mol CO2, 1.2 mol H2 and 0.03 mol acetoin. After fermentation of [3-14C]pyruvate the specific radioactivities of pyruvate, CO2 and acetate were equal to 1:0.01:1. Cellfree extracts contained the following enzymatic activities: pyruvate: ferredoxin (methyl viologen) oxidoreductase (0.2 U mg-1, T=60°C, with Clostridium pasteurianum ferredoxin as electron acceptor; 1.4 U mg-1 at 90°C, with methyl viologen as electron acceptor); acetyl-CoA synthetase (ADP forming) [acetyl-CoA+ADP+Pi⇆acetate+ATP+CoA] (0.34 U mg-1, T=90°C), and hydrogen: methyl viologen oxidoreductase (1.75 U mg-1). Phosphate acetyl-transferase activity, acetate kinase activity, and carbon monoxide:methyl viologen oxidoreductase activity could not be detected. These findings indicate that the archaebacterium P. furiosus ferments pyruvate to acetate, CO2 and H2 involving only three enzymes, a pyruvate:ferredoxin oxidoreductase, a hydrogenase and an acetyl-CoA synthetase (ADP forming).