Purification of NADPH dehydrogenase from a hyperthemophile, Pyrobaculum islandicum

A NADPH dehydrogenase was purified from the hyperthermophilic archaeon, Pyrobaculum islandicum. The membrane protein was solubilized by treatment with 1% Tween 20, and purified 258-fold from the cell-free extract to homogeneity as judged by SDS-PAGE analysis. The molecular mass of the enzyme was revealed to be 41 kDa both by SDS-PAGE and gel filtration analyses. The optimal pH and temperature were 7.0 and above 80°C, respectively. The Km and Vmax values were 0.69 mM and 0.25 nmol/min, respectively. It was suggested that NADPH is an electron donor in the P. islandicum electron transfer system.