Selenophosphates

Glass et al. [93GLA/S1N] recorded the pH-dependent P-NMR chemical shift of H3SeP03 and concluded that the protonation constants, log, K, and log,o K2, of the selenophosphate ion could be estimated to be 8.8 and 4.6, respectively. However, these 

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Reaction with Selenium Nucleophiles. The reactions of selenium nucleophiles are similar to those of the sulfur nucleophiles selenophosphates can be aminoaLkylated (135). A dihydroselenazine has been obtained by reaction of diethyl ketone, elementary selenium, and ethyleneimine (136). 

We were one of the first groups to report a ternary selenophosphate of a rare-earth metal [11-13]. Since that time, we have uncovered a host of rare-earth metal chalcophosphates [1, 13, 14] that complement the transition-metal compounds found by the Kanatzidis group [15-31]. Despite the host of publications in the area of metal chalcophosphate chemistry, there have only been our systematic studies of the quaternary phase space of the rare-earth metal chalcophosphates [1, 13, 14]. 

The chemistry and the structures in this report have been organized by the main-group/chalcogen building block units (Fig. 14.1). At the start of 2000, we were beginning to understand aspects of the chemistry of chalcophosphates both as selenophosphates and thiophosphates. The thesis of Dr. Carl Evenson [14] and his subsequent papers discuss the composition phase diagrams of Y,... 

Figure 28-12. Selenocysteine (top) and the reaction catalyzed by selenophosphate synthetase (bottom).

A similar reaction of methyl P-D-ribopyranoside (5) with P(NMe2)3 in dioxane gave 2,3,4-bicyclophosphite of P-methyl-D-ribopyranoside, 6a in 90% yield. It was sulfurated and selenated to give the corresponding thiophosphate 6b and selenophosphate 6c in 89 and 81% yields, respectively. Oxidation of 6a with hydrogen peroxide gave cyclic phosphate 6d (92%), whereas its hydrolysis in aqueous... 

All selenium-containing proteins and enzymes in animals, microorganisms and plants incorporate selenocysteine non-specifically105 or as part of Se-dependent antioxidant enzymes such as glutathione peroxidase, (EC 1.11.1.9) which has a Se-cysteine residue in its active site.116 120 An active form of Se, selenophosphate, is produced by selenophosphate synthetase in several bacteria. This active form is required for the production of Secys-tRNA, a precursor for Se-cysteine.121 In a similar vein, a Se-containing modified-tRNA nucleoside, 5-methylaminomethyl-2-selenouridine, encodes a selenouridine synthase which replaces sulfur in tRNA with selenium.122... 

Confirmation of the role of selenophosphate and discovery of selenouridine synthase 139... 

Figure 1 Overview of specific use of seienium in bioiogical systems. Selenium can be incorporated into macromolecules in at least three separate pathways. From the reduced form of selenide, selenium is activated to selenophosphate by the action of the enzyme selenophosphate synthetase (SPS or SelD). This activated form is then used as a substrate for pathway-specific enzymes that lead to (1) insertion as selenocysteine into proteins during translation (selenoproteins), (2) incorporation into tRNA molecules as mnm Se U or Se U, and (3) insertion into a unique class of molybdoenzymes as a labile, but required, cofactor. The need for activation to selenophosphate has been demonstrated in all cases at the genetic and biochemical level, with the exception of the labile selenoenzymes, where activation of selenium has only been proposed based on proximity of genes within an operon encoding SPS and a molybdoenzyme. ...

Selenophosphate synthetase Selenoprotein synthesis Escherichia coli 96-98... 

Deiodonase 1 Deiodonase 2 Deiodonase 3 Selenophosphate synthetase 2 Selenoprotein P Selenoprotein W Selenoprotein H Selenoprotein I Selenoprotein K Selenoprotein M Selenoprotein N Selenoprotein O Selenoprotein R (MsrB) Selenoprotein S Selenoprotein T Selenoprotein V Sept 5 (15kDa selenoprotein)... 

The author hopes that this chapter has convinced the readers of the value of homogeneous catalysis for the synthesis of organophosphorus compounds and for organo-heteroatom compounds in a broader sense. Hydrosilylation and hydroboration are indispensable modern synthetic reactions in this category. The H-P addition reactions herein described joins them as a third member. Although this chapter does not cover, the addition reactions of the S-P and Se-P bonds in thiophosphates [39] and selenophosphates [40] to alkynes also proceed in the presence of transition metal catalysts. In view of the wide use of phosphorus compounds, the new procedures will find practical applications. 

This magnesium-dependent enzyme [EC 2.7.9.3], also known as selenide,water dikinase and selenium donor protein, catalyzes the reaction of ATP with selenide and water to produce AMP, selenophosphate, and orthophosphate. 

This enzyme [EC 2.9.1.1], also known as selenocysteine (or SeC) synthase, L-selenocysteinyl-tRNA(SeC) synthase, L-selenocysteinyl-tRNA(Sel) synthase, cysteinyl-tRNA(SeC)-selenium transferase, and cysteinyl-tRNA-(Sel)-selenium transferase, catalyzes the reaction of L-seryl-tRNA and selenophosphate to form L-selenocys-teinyl-tRNA(SeC), orthophosphate, and water. The enzyme is responsible for the insertion of selenocysteine into selenoproteins. See L-Selenocysteine... 

RNA POLYMERASES SELENOPHOSPHATE SYNTHETASE SHIKIMATE KINASE SULFATE ADENYLYLTRANSFERASE TUBULIN TYROSINE LIGASE UBIQUITIN-PROTEIN LIGASES d-XYLULOKINASE ATP-dependent protease La,... 

SELENOPHOSPHATE SYNTHETASE STARCH PHOSPHORYLASE SUCCINYL-CoA SYNTHETASE SUCROSE PHOSPHORYLASE TUBULIN.TYROSINE LIGASE ORTHOPHOSPHATE CONTINUOUS ASSAY Orthovanadate,... 

SELENOPHOSPHATE SYNTHETASE SELENOPHOSPHATE SYNTHETASE SELF-ABSORPTION Self-activating process,... 

A-Alkyl-2,1,3-benzoselenadiazolium salts react with sodium hydroxide with elimination of selenium to give A-monoalkyl-o-phenylenediamines <89SC1381>. The thiaselenazolines (38a) and the diselenazolines (38b) are attacked by trialkyl phosphites at Se with elimination of selenophosphate and incorporation of phosphorus into the ring (87) in place of selenium (Equation (8)) <80CB2699>. 

Selenophosphates and Oxyselenophosphates.—By the action of phosphorus pentaselenide on aqueous solutions of the selenides of... 

Thiocysteine can also arise in a similar manner through action of cystathionine (3 lyase on cystine. Thiocysteine is eliminated with production of pyruvate and ammonia from the rest of the cystine molecule 467 One of the nifS-like proteins of E. coli is thought to transfer a selenium atom from selenocysteine (pp. 823-827) into selenophosphate 466a f The latter can be formed by transfer of a phospho group from ATP to selenide HSe-. The other products of ATP cleavage are AMP and P . Reduction of Se° to HSe- is presumably necessary. 

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