title: The bifunctional pyruvate decarboxylase/pyruvate ferredoxin oxidoreductase from Thermococcus guaymasensis.
abstract: The hyperthermophilic archaeon Thermococcus guaymasensis produces ethanol as a metabolic end product, and an alcohol dehydrogenase (ADH) catalyzing the reduction of acetaldehyde to ethanol has been purified and characterized. However, the enzyme catalyzing the formation of acetaldehyde has not been identified. In this study an enzyme catalyzing the production of acetaldehyde from pyruvate was purified and characterized from T. guaymasensis under strictly anaerobic conditions. The enzyme had both pyruvate decarboxylase (PDC) and pyruvate ferredoxin oxidoreductase (POR) activities. It was oxygen sensitive, and the optimal temperatures were 85°C and >95°C for the PDC and POR activities, respectively. The purified enzyme had activities of 3.8 ± 0.22 U mg(-1) and 20.2 ± 1.8 U mg(-1), with optimal pH-values of 9.5 and 8.4 for each activity, respectively. Coenzyme A was essential for both activities, although it did not serve as a substrate for the former. Enzyme kinetic parameters were determined separately for each activity. The purified enzyme was a heterotetramer. The sequences of the genes encoding the subunits of the bifunctional PDC/POR were determined. It is predicted that all hyperthermophilic β -keto acids ferredoxin oxidoreductases are bifunctional, catalyzing the activities of nonoxidative and oxidative decarboxylation of the corresponding β -keto acids.
authors: Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1 ; Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada M5G 1L7.
authors: Mohammad S
authors: 0000-0003-4379-8158
authors: MS
authors: Eram
authors: Department of Chemistry and Physics, Roger Williams University, One Old Ferry Road, Bristol, RI 02809, USA.
authors: Erica
authors: 0000-0001-9298-5721
authors: E
authors: Oduaran
authors: Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1.
authors: Kesen
authors: 0000-0001-6249-9298
authors: K
authors: Ma
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism; D019641:DNA, Archaeal / Q000737:chemistry / Q000235:genetics; D004791:Enzyme Inhibitors / Q000378:metabolism; D004795:Enzyme Stability; D000431:Ethanol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D055503:Protein Multimerization; D011767:Pyruvate Decarboxylase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D050743:Pyruvate Synthase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013696:Temperature; D019712:Thermococcus / Q000201:enzymology* / Q000235:genetics
chemical_list: D019641:DNA, Archaeal; D004791:Enzyme Inhibitors; D000431:Ethanol; D019289:Pyruvic Acid; D050743:Pyruvate Synthase; D011767:Pyruvate Decarboxylase; D000079:Acetaldehyde; D010100:Oxygen