Some properties of formate dehydrogenase, accumulation and incorporation of 185W-tungsten into proteins of Clostridium formicoaceticum

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Abstract
Formate dehydrogenase of Clostridium formicoaceticum used only methyl and benzyl viologen, but not NAD as electron acceptor. The S0.5 values were 0.9×10-4 M for formate and 5.8×10-3 M for methyl viologen. Using potassium phosphate buffer a pH-optimum of 7.9 was observed. The initial velocity of the formate dehydrogenase activity reached a maximum at 70°C, whereas the activity was stable only up to 50°C. The level of formate dehydrogenase in C. formicoaceticum was increased to its maximum when 10-6 M selenite and 10-7 M tungstate were added to a synthetic medium. Addition of molybdate instead of tungstate did not increase the level of formate dehydrogenase. 185W-tungsten was concentrated about 100-fold by C. formicoaceticum; molybdate had no major effect on the uptake of tungsten. 185W-tungsten was found almost exclusively in the soluble fluid and was predominantly recovered after chromatography in a protein of about 88000 molecular weight. Occasionally a labelled protein of low molecular weight was observed. Again molybdate added even in high molar excess did not influence the labelling pattern. No radioactivity peak could be obtained at the elution peak of formate dehydrogenase activity. The extreme instability of formate dehydrogenase prevented further purification.