Formate dehydrogenase (EC 1.2.1.2) from Pseudornonas oxalaticus has been isolated and characterized. The enzyme (molecular weight 31 5 000) is a complex flavoprotein containing 2 FMN, 18-25 non-heme iron atoms and 15-20 acid-labile sulphides. In the last step of the purification, a sucrose gradient centrifugation, a second catalytically active species has been found apparently originating from a dissociation of the enzyme into two equal subunits. The enzyme is specific toward its natural substrate formate. It transfers electrons to NAD', oxygen, ferricyanide, and a lot of nonphysiological acceptors (dyes). In addition electrons are transferred from NADH to these acceptors.The (reversible) removal of FMN requires a reduction step. Reincorporation has been followed by the reappearance of the reactivity against formate and by fluorescence titration. The deflavo enzyme also binds FAD and riboflavin. The resulting enzyme species show characteristic catalytic abilities. Activity against formate is peculiar to the FMN species.When the aerobic bacterium Pseudornonas osalati-L'US is grown on formate as the main carbon source, the oxidation of formate to COZ is the key process for obtaining energy and reducing equivalents. The key enzyme for the latter is formate dehydrogenase, a complex flavoprotein containing FMN, iron and labile sulphur. It catalyzes the reaction HCOF + NAD' COz + NADH. (1) The C02 formed is incorporated predominantly into the ribulose 1,5-bisphosphate cycle as in autotrophic organisms [I, 21. The observation that a cosubstrate (pyruvate or acetate) is needed for growth on formate [3] has not been related to the carbon metabolism of the organism so far.In an earlier paper [4] we reported that the attainment of the thermodynamically expected equilibrium (1) is catalyzed by the enzyme in both directions and that COZ is reduced to formate by NADH under catalysis of the enzyme. COZ (not bicarbonate) has been identified as the active species in this equilibrium.As observed for all other complex flavoproteins, formate dehydrogenase catalyzes several other nonphysiological oxidation/reduction reactions because its chromophoric groups interact with various electron donors and acceptors : dyes, oxygen, ferricyanide. The resulting reactions can be separated into two groups,

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Das Erstellen und Weitergeben von Kopien dieses PDFs ist nicht zulässig. * Den Herausgebern danke ich für wertvolle Kommentare. 1 Vgl. Losurdo 2010. Dass mit Losurdo ausgerechnet ein Apologet des Stalinismus, also jener totalen Herrschaft, die zum schlechten Ruf des Sozialismus gleichermaßen wie zum guten des Liberalismus beitrug, die verdrängte Geschichte des letzteren schreibt, soll nicht unerwähnt bleiben. Losurdos eigene politische Position ist anti-emanzipatorisch. Sie nimmt aber seiner "Gegengeschichte" des Liberalismus nicht ihren wissenschaftlichen Wert.

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