Effects of Molybdate, Tungstate, and Selenium Compounds on Formate Dehydrogenase and Other Enzyme Systems in Escherichia coli

Abstract

The role of selenium and molybdenum in the metabolism of Escherichia coli was explored by growing cells in a simple salts medium and examining the metabolic consequences of altering the concentration of molybdenum and selenium compounds in the medium. The addition of tungstate increased the molybdate deficiency of this medium, as reflected by lowered levels of enzyme systems previously recognized to require compounds of molybdenum and selenium for their formation [formate-dependent oxygen reduction, formate dehydrogenase (FDH) (EC 1.2.2.1), and nitrate reductase (EC 1.9.6.1)]. The requirement for selenium and molybdenum appears to be unique to the enzymes of formate and nitrate metabolism since molybdateand selenite-deficient medium had no effect on the level of several dehydrogenase and oxidase systems, for which the electron donors were reduced nicotinamide adenine dinucleotide, succinate, Dor L-lactate, and glycerol. In addition, no effect was observed on the growth rate or cell yield with any carbon source tested (glucose, glycerol, DL-lactate, acetate, succinate, and L-malate) when the medium was deficient in molybdenum and selenium. DL-Selenocystine was about as effective as selenite in stimulating the formation of formate dehydrogenase, whereas DL-selenomethionine was only 1% as effective. In aerobic cells, an amount of FDH was formed such that 3,200 or 3,800 moles of formate were oxidized per min per mole of added selenium (added as DL-selenocystine or selenite, respectively).Selenium has been implicated as an essential trace element in the nutrition of animals and some species of plants. Schwarz (23) has found that selenite and an as yet uncharacterized organic selenium compound from natural sources (factor-3) are effective in preventing experimental nutritional liver diseases and death in rats. Thompson and Scott (30) have shown that a diet deficient only in selenium is fatal in chicks. Oldfield et al. (16) have shown that dietary selenium prevents white muscle disease in sheep. Trelease and Trelease (31) reported that selenium is required for normal growth and development in the selenium indicator species of Astragalus (vetch). However, neither the molecular basis of selenium requirement nor its functional form is known. One theory holds that this element functions in the cell as an antioxidant (28, 29), but ' This work represents part of a doctoral dissertation to be submitted by H.G.E. to the

CO2 reductase from Clostridium pasteurianum: Molybdenum dependence of synthesis and inactivation by cyanide

“…pasteurianum most probably is a molybdoenzyme: It is synthesized only in the presence of molybdenum and is inactivated by low concentrations of cyanide, as are other molybdoenzymes. A dependence of CO 2 reductase synthesis on selenium, as has been reported for the formate dehydrogenase from Escherichia coli [7][8][9][10][11], is definitely ruled out.…”

“…Formate dehydrogenase formation inE. coli is known to be dependent on both molybdenum and selenium [7][8][9][10][11]. Therefore it was of interest to determine.the effect of these trace elements on CO 2 reductase synthesis in Cl.…”

Tungsten, the Surprisingly Positively Acting Heavy Metal Element for Prokaryotes

“…42,43 These results stood in sharp contrast to studies using E. coli that showed a strict requirement for molybdate and selenite to express an active FDH if the organism is grown in a defined medium, whereas addition of tungstate is a strong antagonist for FDH activity. 16,44 Until that time, tungstate was supposed to act only as an inhibitor for molybdoenzymes, such as nitrate reductase, xanthine dehydrogenase, aldehyde oxidase, and sulfite oxidase. 4,45 Thus, only a few people became convinced that tungstate even acts positively on a biological system.…”

Editing of the gut microbiota reduces carcinogenesis in mouse models of colitis-associated colorectal cancer

“…E. coli expresses three nitrate reductases and two respiratory formate dehydrogenases to facilitate this disease-associated metabolism (Unden and Dünnwald, 2008). All of these enzymes are metalloenzymes with a molybdenum cofactor (MoCo) in their active site (Enoch and Lester, 1972). In the presence of excess amounts of tungsten ions (W), tungsten is incorporated into the molybdopterin cofactor (Nichols and Rajagopalan, 2005).…”