Purification and Characterization of a Thermostable Pyruvate Ferredoxin Oxidoreductase/Pyruvate Decarboxylase from Thermococcus kodakaraensis

Thermococcus kodakaraensis is a strictly anaerobic sulfur dependent archaeon that grows optimally at 85 degrees C by a fermentative type metabolism. An extremely thermostable bifunctional enzyme, which exhibits pyruvate ferredoxin oxidoreductase (POR) and pyruvate decarboxylase (PDC) activities, was purified to an apparent homogeneity from this archaeon. The purified enzyme exhibited optimal activities at 95 degrees C for POR and 90 degrees C for PDC reactions. The optimum pH for POR reaction was 8.5 and for that of PDC it was 9.5, in the absence of oxygen. The specific activities for POR and PDC reactions were 22 U/mg and 3.8 U/mg, respectively. The native enzyme had an apparent molecular weight of 240 kDa and was a dimer of heterotetramers (alpha beta gamma delta)(2) with molecular masses of 44, 36, 20 and 12 kDa, respectively. Both of the activities were oxygen sensitive. The apparent K-m values for POR reaction towards pyruvate and CoASH were 0.49 mu M and 115 mu M, respectively, while for PDC reaction values these values were mu M 0.34 and 42 mu M. To the best of our knowledge this is the first report on purification and characterization of a POR/PDC from T. kodakaraensis.