Tungsten, the Surprisingly Positively Acting Heavy Metal Element for Prokaryotes

Abstract

The history and changing function of tungsten as the heaviest element in biological systems is given. It starts from an inhibitory element/anion, especially for the iron molybdenum-cofactor (FeMoCo)-containing enzyme nitrogenase involved in dinitrogen fixation, as well as for the many "metal binding pterin" (MPT)-, also known as tricyclic pyranopterin- containing classic molybdoenzymes, such as the sulfite oxidase and the xanthine dehydrogenase family of enzymes. They are generally involved in the transformation of a variety of carbon-, nitrogen- and sulfur-containing compounds. But tungstate can serve as a potential positively acting element for some enzymes of the dimethyl sulfoxide (DMSO) reductase family, especially for CO(2)-reducing formate dehydrogenases (FDHs), formylmethanofuran dehydrogenases and acetylene hydratase (catalyzing only an addition of water, but no redox reaction). Tungsten even becomes an essential element for nearly all enzymes of the aldehyde oxidoreductase (AOR) family. Due to the close chemical and physical similarities between molybdate and tungstate, the latter was thought to be only unselectively cotransported or cometabolized with other tetrahedral anions, such as molybdate and also sulfate. However, it has now become clear that it can also be very selectively transported compared to molybdate into some prokaryotic cells by two very selective ABC-type of transporters that contain a binding protein TupA or WtpA. Both proteins exhibit an extremely high affinity for tungstate (K(D) < 1 nM) and can even discriminate between tungstate and molybdate. By that process, tungsten finally becomes selectively incorporated into the few enzymes noted above.

Dual effects of sodium tungstate on adipocyte biology: inhibition of adipogenesis and stimulation of cellular oxygen consumption

“…In fact, it has been classically used as an oxidizing agent in organic chemistry 19,20 and may act as a co-factor activating or inhibiting some oxidizing enzymes. [21][22][23] In vivo, sodium tungstate decreases the oxidation state of brown adipose tissue proteins and modulates several redox proteins both in white and brown adipose tissues. 6,7 In order to assess whether sodium tungstate modulates the redox state of our system, we performed oxidation assays of proteins from 3T3-F442A cells chronically treated with sodium tungstate.…”

A Life with Acetogens, Thermophiles, and Cellulolytic Anaerobes

“…The enzyme consists of two subunits with the composition α 2 β 2 , two selenocysteins residing in the α-subunits, two tungstens released by denaturation of the enzyme as a fluorescent tungsten cofactor similar to the molybdenum cofactor of several molybdenum enzymes, and potential binding sites for 48 iron-forming [4Fe-4S] and [2Fe-2S] clusters. Tungsten has now been found in many mainly thermophilic microorganisms, and the biological importance of tungsten has recently been reviewed (3). With the purification of the formate dehydrogenase all enzymes of the acetyl-CoA pathway for acetate synthesis from CO 2 had been purified.…”

Impact of Sodium Tungstate and Tungsten Alloys on the Growth of Selected Microorganisms with Environmental Significance

“…Highly polluted environments are often characterized by harsh conditions preventing or enhancing the activity/growth of most potentially useful microorganisms. Previous studies reveal limited and conflicting data regarding the effect of tungsten on microorganisms, where it has been attributed to both positive and negative effects on microbial growth (Sugio et al, 2001, Strigul et al, 2005, Andreesen and Makdessi, 2008.…”

“…Some bacterial species are suggested to thrive in the presence of tungsten, including some Clostridia and methanogenic archaea (Andreesen and Makdessi, 2008;Klezin and Adams, 1996). This positive effect may be attributed to enzymes, including those of the aldehyde oxidoreductase (AOR) family, that require tungsten (Andreesen and Makdessi, 2008).…”