“…Further aspects of the chemistry, biochemistry and biosynthesis of the pterin cofactor of molybdoenzymes will not be discussed here since these topics have been reviewed repeatedly (see above) and for more recent literature the reader is referred to Refs. Similarly, there are many reports on synthetic compounds as models for Mo- [15,281,305,318,319] and W-based [280,[320][321][322][323] pterin cofactors. Moreover, in the absence of any data, it is assumed that the pterin biosynthetic pathway and its regulation is the same for tungstoenzymes as it is for molybdoenzymes.…”
Section: The Tungsten-pterin Catalytic Sitementioning
Tungsten (atomic number 74) and the chemically analogous and very similar metal molybdenum (atomic number 42) are minor yet equally abundant elements on this planet. The essential role of molybdenum in biology has been known for decades and molybdoenzymes are ubiquitous. Yet, it is only recently that a biological role for tungsten has been established in prokaryotes, although not as yet in eukaryotes. The best characterized organisms with regard to their metabolism of tungsten are certain species of hyperthermophilic archaea (Pyrococcus furiosus and Thermococcus litoralis), methanogens (Methanobacterium thermoautotrophicum and Mb. wolfei), Gram-positive bacteria (Clostridium thermoaceticum, C. formicoaceticum and Eubacterium acidaminophilum), Gram-negative anaerobes (Desulfovibrio gigas and Pelobacter acetylenicus) and Gram-negative aerobes (Methylobacterium sp. RXM). Of these, only the hyperthermophilic archaea appear to be obligately tungsten-dependent. Four different types of tungstoenzyme have been purified: formate dehydrogenase, formyl methanofuran dehydrogenase, acetylene hydratase, and a class of phylogenetically related oxidoreductases that catalyze the reversible oxidation of aldehydes. These are carboxylic reductase, and three ferredoxin-dependent oxidoreductases which oxidize various aldehydes, formaldehyde and glyceraldehyde 3-phosphate. All tungstoenzymes catalyze redox reactions of very low potential (< -420 mV) except one (acetylene hydratase) which catalyzes a hydration reaction. The tungsten in these enzymes is bound by a pterin moiety similar to that found in molybdoenzymes. The first crystal structure of a tungsten-or pterin-containing enzyme, that of aldehyde ferredoxin oxidoreductase from P. furiosus, has revealed a catalytic site with one W atom coordinated to two pterin molecules which are themselves bridged by a magnesium ion. The geochemical, ecological, biochemical and phylogenetic basis for W-vs. Mo-dependent organisms is discussed.
“…Further aspects of the chemistry, biochemistry and biosynthesis of the pterin cofactor of molybdoenzymes will not be discussed here since these topics have been reviewed repeatedly (see above) and for more recent literature the reader is referred to Refs. Similarly, there are many reports on synthetic compounds as models for Mo- [15,281,305,318,319] and W-based [280,[320][321][322][323] pterin cofactors. Moreover, in the absence of any data, it is assumed that the pterin biosynthetic pathway and its regulation is the same for tungstoenzymes as it is for molybdoenzymes.…”
Section: The Tungsten-pterin Catalytic Sitementioning
Tungsten (atomic number 74) and the chemically analogous and very similar metal molybdenum (atomic number 42) are minor yet equally abundant elements on this planet. The essential role of molybdenum in biology has been known for decades and molybdoenzymes are ubiquitous. Yet, it is only recently that a biological role for tungsten has been established in prokaryotes, although not as yet in eukaryotes. The best characterized organisms with regard to their metabolism of tungsten are certain species of hyperthermophilic archaea (Pyrococcus furiosus and Thermococcus litoralis), methanogens (Methanobacterium thermoautotrophicum and Mb. wolfei), Gram-positive bacteria (Clostridium thermoaceticum, C. formicoaceticum and Eubacterium acidaminophilum), Gram-negative anaerobes (Desulfovibrio gigas and Pelobacter acetylenicus) and Gram-negative aerobes (Methylobacterium sp. RXM). Of these, only the hyperthermophilic archaea appear to be obligately tungsten-dependent. Four different types of tungstoenzyme have been purified: formate dehydrogenase, formyl methanofuran dehydrogenase, acetylene hydratase, and a class of phylogenetically related oxidoreductases that catalyze the reversible oxidation of aldehydes. These are carboxylic reductase, and three ferredoxin-dependent oxidoreductases which oxidize various aldehydes, formaldehyde and glyceraldehyde 3-phosphate. All tungstoenzymes catalyze redox reactions of very low potential (< -420 mV) except one (acetylene hydratase) which catalyzes a hydration reaction. The tungsten in these enzymes is bound by a pterin moiety similar to that found in molybdoenzymes. The first crystal structure of a tungsten-or pterin-containing enzyme, that of aldehyde ferredoxin oxidoreductase from P. furiosus, has revealed a catalytic site with one W atom coordinated to two pterin molecules which are themselves bridged by a magnesium ion. The geochemical, ecological, biochemical and phylogenetic basis for W-vs. Mo-dependent organisms is discussed.
“…Moreover, in the absence of any data, it is assumed that the pterin biosynthetic pathway and its regulation is the same for tungstoenzymes as it is for molybdoenzymes. Similarly, there are many reports on synthetic compounds as models for Mo- [15,281,305,318,319] and W-based [280,[320][321][322][323] pterin cofactors. However, the emphasis in this area might change somewhat in the future, based on the finding that the W site in P. .fi~riosus AOR is coordinated by four S atoms from two pterin molecules.…”
Section: The Tungsten-pterin Catalytic Sitementioning
Tungsten (atomic number 74) and the chemically analogous and very similar metal molybdenum (atomic number 42) are minor yet equally abundant elements on this planet. The essential role of molybdenum in biology has been known for decades and molybdoenzymes are ubiquitous. Yet, it is only recently that a biological role for tungsten has been established in prokaryotes, although not as yet in eukaryotes. The best characterized organisms with regard to their metabolism of tungsten are certain species of hyperthermophilic archaea (Pyrococcus furiosus and Thermococcus litoralis), methanogens (Methanobacterium thermoautotrophicum and Mb. wolfei), Gram-positive bacteria (Clostridium thermoaceticum, C. formicoaceticum and Eubacterium acidaminophilum), Gram-negative anaerobes (Desulfovibrio gigas and Pelobacter acetylenicus) and Gram-negative aerobes (Methylobacterium sp. RXM). Of these, only the hyperthermophilic archaea appear to be obligately tungsten-dependent. Four different types of tungstoenzyme have been purified: formate dehydrogenase, formyl methanofuran dehydrogenase, acetylene hydratase, and a class of phylogenetically related oxidoreductases that catalyze the reversible oxidation of aldehydes. These are carboxylic reductase, and three ferredoxin-dependent oxidoreductases which oxidize various aldehydes, formaldehyde and glyceraldehyde 3-phosphate. All tungstoenzymes catalyze redox reactions of very low potential (< -420 mV) except one (acetylene hydratase) which catalyzes a hydration reaction. The tungsten in these enzymes is bound by a pterin moiety similar to that found in molybdoenzymes. The first crystal structure of a tungsten-or pterin-containing enzyme, that of aldehyde ferredoxin oxidoreductase from P. furiosus, has revealed a catalytic site with one W atom coordinated to two pterin molecules which are themselves bridged by a magnesium ion. The geochemical, ecological, biochemical and phylogenetic basis for W-vs. Mo-dependent organisms is discussed.
“…strong π-acids and π-bases, have attracted growing attention. − This communication describes the synthesis, characterization, and reactivity of carbonyl(η 2 -nitrile)tungsten(II), carbonyloxotungsten(IV), and carbonylthiotungsten(IV) complexes ( A − C ; L = hydrotris(3,5-dimethylpyrazol-1-yl)borate, X = monoanion) which combine π-acid carbonyl and π-base nitrile or chalcogenido ligands at a common metal center. These novel complexes have emerged from the development of a low-valent synthetic approach to bis(chalcogenido)tungsten(VI) complexes which involves successive two-electron-oxidation/atom-transfer reactions, beginning with [LW 0 (CO) 3 ] - , and progressing through LW II X(CO) x ( x = 2, 3), 5,9-12 LW II X(η 2 -RCN)(CO) (R = Me, Et, Ph), and LW IV EX(CO) (E = O, S) to LW VI E 2 X. , Quality (non-disordered) crystal structures of LW II (S 2 PR* 2 -S )(η 2 -MeCN)(CO) (R* = (−)-mentholate), LW IV O(S 2 PPh 2 -S )(CO), and LW IV S(S 2 PPh 2 -S )(CO) confirm the formulations and provide the first definitive metrical data for the metal cores in A − C , the structure of LW IV S(S 2 PPh 2 )(CO) being the first reported for any carbonylthiometal complex. …”
Reactions of
LW(S2PR2)(CO)2 (L
= hydrotris(3,5-dimethylpyrazol-1-yl)borate) with pyridine
N-oxide
produce carbonyl oxo complexes,
LWIVO(S2PR2)(CO).
Thermal decarbonylation of LWX(CO)2 (X =
halide)
complexes in organonitrile solvents produces 4-electron-donor nitrile complexes, LWIIX(η2-RCN)(CO),
which
react with NH4[S2PR2] to
form
LWII(S2PR2)(η2-RCN)(CO). Reactions of the nitrile complexes with
propylene
sulfide result in high yields of the carbonyl thio complexes LWIVSX(CO) or
LWIVS(S2PR2)(CO). The
structures of LWIVO(S2PPh2)(CO),
(R)-LWII(S2PR*2)(η2-MeCN)(CO) (R* = (−)-mentholate), and
LWIVS(S2PPh2)(CO)
can be rationalized in terms of the π-bonding requirements of the electronically disparate π-acid and π-base
ligands.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
