In chemistry, an arsenite is a chemical compound containing an arsenic oxyanion where arsenic has oxidation state +3. Note that in fields that commonly deal with groundwater chemistry, arsenite is used generically to identify soluble As anions. IUPAC have recommended that arsenite compounds are to be named as arsenate(III), for example ortho-arsenite is called trioxidoarsenate(III). Ortho-arsenite contrasts to the corresponding anions of the lighter members of group 15, phosphite which has the structure HPO 2− 3 and nitrite , NO − 2 which is bent.
21-585: A number of different arsenite anions are known: In all of these the geometry around the As centers are approximately trigonal, the lone pair on the arsenic atom is stereochemically active. Well known examples of arsenites include sodium meta-arsenite which contains a polymeric linear anion, (AsO − 2 ) n , and silver ortho-arsenite, Ag 3 AsO 3 , which contains the trigonal AsO 3− 3 anion. Some arsenite salts can be prepared from an aqueous solution of As 2 O 3 . Examples of these are
42-465: A complex polymeric anion); schneiderhöhnite , Fe Fe 3 (AsO 3 )(As 2 O 5 ) 2 ; magnussonite , Mn 5 (OH)(AsO 3 ) 3 ; trippkeite , CuAs 2 O 4 ; trigonite , Pb 3 Mn(AsO 3 ) 2 (HAsO 3 ) ; tooeleite , Fe 6 (AsO 3 ) 4 (SO 4 )(OH) 4 ·4H 2 O . Arsenic can enter groundwater due to naturally occurring arsenic at deeper levels or from mine workings. Arsenic(III) can be removed from water by
63-486: A mechanism of activation of TPP coenzyme by forming the conserved hydrogen bond with glutamate residue (Glu59 in human E1) and by imposing a V-conformation that brings the N4’ atom of the aminopyrimidine to intramolecular hydrogen bonding with the thiazolium C2 atom. This unique combination of contacts and conformations of TPP leads to formation of the reactive C2-carbanion, eventually. After the cofactor TPP decarboxylates pyruvate,
84-442: A metallic or garlic taste, stomach pain, nausea, vomiting, diarrhea, convulsions, decreased blood pressure, and headache. Severe acute poisoning may lead to nervous system damage resulting in weakness, poor coordination, or “pins and needles” sensations, eventual paralysis, and death. Sodium arsenites are primarily used as a pesticide , but has other uses such as hide preservative, antiseptic , dyeing, and soaps. Sodium arsenite
105-447: A number of methods, oxidation of As to As for example with chlorine followed by coagulation with for example iron(III) sulfate. Other methods include ion-exchange and filtration. Filtration is only effective if arsenic is present as particulates, if the arsenite is in solution it passes through the filtration membrane. Sodium arsenite is used in the water gas shift reaction to remove carbon dioxide. Fowler's solution first introduced in
126-409: Is an appropriate chemical stressor to induce the production of heat shock proteins , and the formation of cytoplasmic stress granules. Sodium arsenite can be used as a reducing agent in organic chemistry, as it is able to reduce a trihaloalkane to a dihaloalkane: The LD 50 (oral, mouse) is 40 mg/kg. Pyruvate dehydrogenase Pyruvate dehydrogenase is an enzyme that catalyzes
147-580: Is crucial because acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration . To distinguish between this enzyme and the PDC, it is systematically called pyruvate dehydrogenase (acetyl-transferring) . The thiamine pyrophosphate (TPP) converts to an ylide by deprotonation. The ylide attack the ketone group of pyruvate. The resulting adduct decarboxylates . The resulting 1,3-dipole reductively acetylates lipoamide-E2. In terms of details, biochemical and structural data for E1 revealed
168-599: Is important regulator of premyelocytic immune cell development, differentiation, and apoptosis. Some species of bacteria obtain their energy by oxidizing various fuels while reducing arsenates to form arsenites. The enzymes involved are known as arsenate reductases . In 2008, bacteria were discovered that employ a version of photosynthesis with arsenites as electron donors , producing arsenates (just like ordinary photosynthesis uses water as electron donor, producing molecular oxygen). The researchers conjectured that historically these photosynthesizing organisms produced
189-468: Is produced by treating arsenic trioxide with sodium carbonate or sodium hydroxide . Sodium arsenite is amorphous , typically being obtained as a powder or as a glassy mass. [REDACTED] Sodium arsenite can be inhaled or absorbed through the skin. Along with its known carcinogenic and teratogenic effects, contact with the substance can yield symptoms such as skin irritation, burns, itching, thickened skin, rash, loss of pigment, poor appetite,
210-591: Is reversed by pyruvate dehydrogenase phosphatase , which is stimulated by insulin , PEP , and AMP , but competitively inhibited by ATP , NADH , and Acetyl-CoA . Pyruvate dehydrogenase is targeted by an autoantigen known as anti-mitochondrial antibodies (AMA), which results in progressive destruction of the small bile ducts of the liver, leading to primary biliary cirrhosis . These antibodies appear to recognize oxidized protein that has resulted from inflammatory immune responses. Some of these inflammatory responses could be related to gluten sensitivity as over 50% of
231-428: The inorganic compound with the formula NaAsO 2 . Also called sodium meta -arsenite, it is an inorganic polymer consisting of the infinite chains [AsO 2 ] n associated with sodium cations , Na . The polymer backbone has the connectivity -O-As(O )-. backbone. Sodium ortho -arsenite is Na 3 AsO 3 . Both compounds are colourless solids. A mixture of sodium meta -arsenite and sodium ortho -arsenite
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#1732773089473252-606: The 18th century was made up from As 2 O 3 as a solution of potassium meta-arsenite, KAsO 2 . Arsenic in its trioxide, As 2 O 3 , (brand name Trisenox, ATO) is used as a chemotherapy drug against acute promyelocytic leukaemia (APL) , a type of myeloid leukemia. The detailed mechanism of action is unknown, but it is suspected to speed up apoptosis of cancer cells. Arsenic trioxide triggers morphological changes and DNA fragmentations in NB4 in vitro model for APL. It also degrades retinoic acid receptor alpha (RARA) . RARA gene
273-555: The acetyl portion becomes a hydroxyethyl derivative covalently attached to TPP. E1 is a multimeric protein. Mammalian E1s, including human E1, are tetrameric, composed of two α- and two β- subunits. Some bacterial E1s, including E1 from Escherichia coli , are composed of two similar subunits, each being as large as the sum of molecular masses of α- and β- subunits. E1 has two catalytic sites, each providing thiamine pyrophosphate ( TPP ) and magnesium ion as cofactors. The α- subunit binds magnesium ion and pyrophosphate fragment while
294-495: The active site. The amino acids are shown as wires, and the TPP is in ball and stick form. The active site also aids in the transfer of the acyl on the TPP to a lipoamide waiting on E2. Phosphorylation of E1 by pyruvate dehydrogenase kinase (PDK) inactivates E1 and subsequently the entire complex. PDK is inhibited by dichloroacetic acid and pyruvate , resulting in a higher quantity of active, unphosphorylated PDH. Phosphorylation
315-517: The acute liver failure patients in one study exhibited a nonmitochondrial autoantibody against tissue transglutaminase . Other mitochondrial autoantigens include oxoglutarate dehydrogenase and branched-chain alpha-keto acid dehydrogenase complex , which are antigens recognized by anti-mitochondrial antibodies . Increased pyruvate dehydrogenase (PDH) activity can cause oncogene-induced cellular senescence , as well as promoting aging. Decreased activity of mitochondrial PDH with age has been shown in
336-454: The arsenates that allowed the arsenate-reducing bacteria to thrive. In humans, arsenite inhibits pyruvate dehydrogenase (PDH complex) in the pyruvate - acetyl CoA reaction, by binding to the –SH group of lipoamide , a participant coenzyme. It also inhibits the oxoglutarate dehydrogenase complex by the same mechanism. The inhibition of these enzymes disrupts energy production. Sodium arsenite Sodium arsenite usually refers to
357-463: The citric acid cycle due to PDH deficiency deprives the body of energy and leads to an abnormal buildup of lactate. PDH deficiency is a common cause of lactic acidosis in newborns and often presents with severe lethargy, poor feeding, tachypnea, and cases of death have occurred. Human proteins that possess pyruvate dehydrogenase activity include: In bacteria , a form of pyruvate dehydrogenase (also called pyruvate oxidase, EC 1.2.2.2) exists that links
378-453: The heart as well as in certain regions of the brain (the striatum and brainstem ). Pyruvate dehydrogenase (PDH) deficiency is a congenital degenerative metabolic disease resulting from a mutation of the pyruvate dehydrogenase complex (PDC) located on the X chromosome. While defects have been identified in all 3 enzymes of the complex, the E1-α subunit is predominantly the culprit. Malfunction of
399-473: The meta-arsenite salts and at low temperature, hydrogen arsenite salts can be prepared, such as Na 2 H 2 As 4 O 8 , NaAsO 2 ·4H 2 O , Na 2 HAsO 3 ·5H 2 O and Na 5 (HAsO 3 )(AsO 3 )·12H 2 O . A number of minerals contain arsenite anions: reinerite , Zn 3 (AsO 3 ) 2 ; finnemanite , Pb 5 Cl(AsO 3 ) 3 ; paulmooreite , Pb 2 As 2 O 5 ; stenhuggarite , CaFeSbAs 2 O 7 (contains
420-472: The reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide . The conversion requires the coenzyme thiamine pyrophosphate . Pyruvate dehydrogenase is usually encountered as a component, referred to as E1, of the pyruvate dehydrogenase complex (PDC). PDC consists of other enzymes, referred to as E2 and E3. Collectively E1-E3 transform pyruvate , NAD , coenzyme A into acetyl-CoA , CO 2 , and NADH. The conversion
441-559: The β-subunit binds pyrimidine fragment of TPP , forming together a catalytic site at the interface of subunits. The active site for pyruvate dehydrogenase (image created from PDB : 1NI4 ) holds TPP through metal ligation to a magnesium ion (purple sphere) and through hydrogen bonding to amino acids. While over 20 amino acids can be found in the active site, amino acids Tyr 89, Arg 90, Gly 136, Val 138, Asp 167, Gly 168, Ala 169, Asn, 196, and His 263 actually participate in hydrogen bonding to hold TPP and pyruvate (not shown here) in
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