Utilization of 2-aminoethylarsonic acid in Pseudomonas aeruginosa

Reinvent Aliphatic Arsenicals as Reversible Covalent Warheads toward Targeted Kinase Inhibition and Non-acute Promyelocytic Leukemia Cancer Treatment

The success of arsenic in acute promyelocytic leukemia (APL) treatment is hardly transferred to non-APL cancers, mainly due to the low selectivity and weak binding affinity of traditional arsenicals to oncoproteins critical for cancer survival. We present herein the reinvention of aliphatic trivalent arsenicals (As) as reversible covalent warheads of As-based targeting inhibitors toward Bruton's tyrosine kinase (BTK). The effects of As warheads' valency, thiol protection, methylation, spacer length, and size on inhibitors' activity were studied. We found that, in contrast to the bulky and rigid aromatic As warhead, the flexible aliphatic As warheads were well compatible with the well-optimized guiding group to achieve nanomolar inhibition against BTK. The optimized As inhibitors effectively blocked the BTK-mediated oncogenic signaling pathway, leading to elevated antiproliferative activities toward lymphoma cells and xenograft tumor. Our study provides a promising strategy enabling rational design of new aliphatic arsenic-based reversible covalent inhibitors toward non-APL cancer treatment.

Preparation of (mono)sulfonates: Suitable precursors for unnatural sulfonolipids

Aiming at the preparation of the novel unnatural, non-isosteric sulfonolipids bearing one, two and three acyl groups 8, 9 and 10, their precursors hydroxyl-containing sulfonates have been prepared from a variety of hydroxyl-containing halogenides and epoxides using the Strecker reaction. Thus, the sulfonates 16 and 22 were prepared pure, while the sulfonate 27 could only be prepared as a by-product using 1,4-dibromo-2,3-butanediol 26 and in low yields. For these reactions, probable pathways leading to the isolated or spectroscopically identified products are proposed. Conclusions about the relative nucleophilicity of SO32- compared to AsO33 - (as well as HO- which is present in their aqueous solutions) were drawn based on the yields of the corresponding arsonic acids and sodium sulfonates. The IR (KBr) and 1H NMR (D2O) spectra of sulfonates (and in some cases of their sulfonic acids) are analyzed and discussed.

Arsenate replacing phosphate: alternative life chemistries and ion promiscuity

A newly identified bacterial strain that can grow in the presence of arsenate and possibly in the absence of phosphate, has raised much interest, but also fueled an active debate. Can arsenate substitute for phosphate in some or possibly in most of the absolutely essential phosphate-based biomolecules, including DNA? If so, then the possibility of alternative, arsenic-based life forms must be considered. The physicochemical similarity of these two oxyanions speaks in favor of this idea. However, arsenate-esters and arsenate-diesters in particular are extremely unstable in aqueous media. Here, we explore the potential of arsenate to be used as substrate by phosphate-utilizing enzymes. We review the existing literature on arsenate enzymology, that intriguingly, dates back to the 1930s. We address the issue of how and to what degree proteins can distinguish between arsenate and phosphate and what is known in general about oxyanion specificity. We also discuss how phosphate-arsenate promiscuity may affect evolutionary transitions between phosphate- and arsenate-based biochemistry. Finally, we highlight potential applications of arsenate as a structural and mechanistic probe of enzymes whose catalyzed reactions involve the making or breaking of phosphoester bonds.

A high yield procedure for the preparation of arsonolipids (2,3-diacyloxypropylarsonic acids)

The crucial step in the preparation of the title arsonolipids starting from the dichloromethane-soluble dithioarsonite CH(2)(OH)CH(OH)CH(2)-As(SPh)(2) is to avoid an internal cyclization during the acylation which protects the primary -OH group from being acylated. This was to a large extent accomplished by using fatty acyl chloride in the presence of the weak base pyridine and controlling the temperature and rate of the acyl chloride addition, giving approximately 70% yields of arsonolipids. The presence of catalytic amounts of 4-dimethylaminopyridine boosted the yields to 82-85%. This yield is a great improvement over the yields (20-55%) previously achieved. The acylating systems (RCO)(2)O or RCOCl and BF(3).Et(2)O gave only moderate yields (25-60%) of arsonolipids.

Preparation of dl-2,3,4-trihydroxybutylarsonic acid and dl-2,3-dihydroxybutane-1,4-bis(arsonic acid): starting compounds for novel arsonolipids

The reaction of DL-1,3-butadiene diepoxide and of DL-1,4-dibromo-2,3-butanediol with aqueous alkaline sodium arsenite, "Na(3)AsO(3)", gave mixtures of the title arsonic acids which can be separated by anion exchange resin. Characterization of by-products leads to a better understanding of these reactions. These compounds are valuable intermediates for the preparation of novel arsonic acids and bis(arsonic acids).

The effect of 2-amino-3-arsonopropionate and 2-amino-4-arsonobutyrate on the development and maintenance of amygdala kindled seizures

The effects of 2-a-3-arsonopropionate and 2-a-4-arsonobutyrate, the arsono analogues of aspartate and glutamate respectively, on the development of electrically-induced kindling in the amygdala, and on seizures induced in fully kindled rats, were compared to the effects of 3-amino-propylarsonate the arsono analogue of GABA. Intra-amygdaloid micro-injection of 2-a-3-arsonopropionate and 2-a-4-arsonobutyrate (10 nmol in 0.5 microl buffer phosphate) reduced the rate of epileptogenesis without preventing the development of generalized seizure responses, after 14 daily stimulations. In fully electrically kindled animals with stage 5 amygdala-kindled seizures, 3-aminopropy-larsonate (10 nmol/0.5 microl) increased after-discharge threshold (ADT) by 82% (P< or =0.005) without having any effect on mean seizure score or after-discharge duration. Chemical reduction of 3-aminopropylarsonate with glutathione diminished the anti-seizure activity of the drug. 2-a-3-arsonopropionate and 2-a-4-arsonobutyrate the arsono analogues of aspartate and glutamate were not effective when they were micro-injected into the amygdala of fully kindled animals at equivalent doses i.e. (10 nmol/0.5 microl). Higher doses (100 nmol/0.5 microl) of 2-a-3-arsonopropionate the analogue of aspartate increased the generalized seizure threshold by 40% (P < or = 0.025), while 2-a-4-arsonobutyrate was not effective even at high doses.

The anti-epileptic effect of 3-aminopropylarsonate on electrically-kindled and N-methyl-D-aspartate-kindled amygdala

The effects of 3-aminopropylarsonate, an arsono analogue of GABA, was tested on the development of electrically-kindled amygdala and on the expression of generalized seizure activity in electrically and NMDA fully amygdala-kindled rats. Intra-amygdaloid microinjection of 3-aminopropylarsonate (10 nmol in 0.5 microl injection vehicle) inhibited electrical epileptogenesis by keeping the seizure score at or below stage 1 on the Racine scale, and the afterdischarge duration (ADD) at or below 19.70 +/- 4.59 s. The effect was reversible after withdrawal of the drug, since the animals developed a generalized seizure activity when kindling stimuli continued in the absence of drug. In fully electrically kindled animals with stage 5 amygdala-kindled seizures, the drug increased afterdischarge threshold (ADT) by 30-70%, without any effect on mean seizure score or ADD. The changes were reversible after 7 days. In fully NMDA-kindled rats, intra-amygdala administration of 3-aminopropylarsonate (10 nmol/0.5 microl) 20 min before injection of NMDA (4 nmol/0.5 microl) reduced the seizure score from 3.80 +/- 0.37(5) on the Racine scale to 0.83 +/- 0.40(6) (P < 0.01). The effect was partially reversible after washing with phosphate buffer. 2-Amino-4-arsonobutyrate, the analogue of glutamate, had no effect on seizure score following treatment with the same concentration of the drug and the same route of injection. The inhibitory effect of 3-aminopropylarsonate on NMDA kindled activity was dose-dependent, since higher doses of NMDA reduced the effect of the drug. The effect of 3-aminopropylarsonate was also selective to NMDA receptors since it had no effect on kainate-induced seizures. With both models of kindling, no gross behavioural abnormalities were observed 3-6 months after treatment with the drug. These findings show the potent antiepileptogenic and anti-convulsant activity of the arsonoanalogue of GABA which appears to be non-toxic and therefore potentially useful as the basis for developing a new family of clinically useful anticonvulsants for treating epilepsy.

Molecular cloning, mapping, and regulation of Pho regulon genes for phosphonate breakdown by the phosphonatase pathway of Salmonella typhimurium LT2

Two pathways exist for cleavage of the carbon-phosphorus (C-P) bond of phosphonates, the C-P lyase and the phosphonatase pathways. It was previously demonstrated that Escherichia coli carries genes (named phn) only for the C-P lyase pathway and that Enterobacter aerogenes carries genes for both pathways (K.-S. Lee, W. W. Metcalf, and B. L. Wanner, J. Bacteriol. 174:2501-2510, 1992). In contrast, here it is shown that Salmonella typhimurium LT2 carries genes only for the phosphonatase pathway. Genes for the S. typhimurium phosphonatase pathway were cloned by complementation of E. coli delta phn mutants. Genes for these pathways were proven not to be homologous and to lie in different chromosomal regions. The S. typhimurium phn locus lies near 10 min; the E. coli phn locus lies near 93 min. The S. typhimurium phn gene cluster is about 7.2 kb in length and, on the basis of gene fusion analysis, appears to consist of two (or more) genes or operons that are divergently transcribed. Like that of the E. coli phn locus, the expression of the S. typhimurium phn locus is activated under conditions of Pi limitation and is subject to Pho regulon control. This was shown both by complementation of the appropriate E. coli mutants and by the construction of S. typhimurium mutants with lesions in the phoB and pst loci, which are required for activation and inhibition of Pho regulon gene expression, respectively. Complementation studies indicate that the S. typhimurium phn locus probably includes genes both for phosphonate transport and for catalysis of C-P bond cleavage.

Arsenite release on enzymic transformation of arsonomethyl substrate analogues: a potentially lethal synthesis by glycerol-3-phosphate dehydrogenase

The isosteric arsenical analogue of glycerol 3-phosphate, 3,4-dihydroxybutylarsonic acid, is a good substrate for rabbit muscle glycerol-3-phosphate dehydrogenase. Its oxidation is accompanied by release of arsenite. This release seems to be due to a spontaneous elimination of arsenite by 3-oxoalkylarsonic acids, as it is also observed in (1) the oxidation of 3-hydroxypropylarsonic acid by yeast alcohol dehydrogenase, (2) treatment of 3,4-dihydroxybutylarsonic acid with periodate and (3) nonenzymic transamination of the glutamate analogue 2-amino-4-arsonobutyric acid. Enzymic formation of 3-oxoalkylarsonic acids in cells can therefore be lethal, as arsenite is poisonous to most organisms because of its high affinity for dithiols such as dihydrolipoyl groups.

Synthesis of 3-arsonopyruvate and its interaction with phosphoenolpyruvate mutase

3-Arsonopyruvate was prepared in four steps from glycine. The arsenic-carbon bond was formed by a Meyer reaction between alkaline arsenite and 2-bromo-3-hydroxy-2-(hydroxymethyl)propionic acid; the 3-arsono-2-hydroxy-2-(hydroxymethyl) propionic acid formed was oxidized with periodate to give 3-arsonopyruvate. This proves to be an alternative substrate for phosphoenolpyruvate mutase, giving pyruvate, which was assayed using lactate dehydrogenase. The K(m) is 20 microM, similar to that observed for the natural substrate phosphonopyruvate (17 microM), whereas the kcat. of 0.01 s-1 was much lower than that for phosphonopyruvate (58 s-1). Arsonopyruvate competitively inhibited the action of the mutase on phosphonopyruvate.

Synthesis of 3-arsonoalanine and its action on aspartate aminotransferase and aspartate ammonia-lyase. Comparison with arsenical analogues of malate and fumarate

DL-3-Arsonoalanine has been synthesized by the Strecker synthesis from the unstable compound arsonoacetaldehyde. It inactivates pig heart cytosolic aspartate aminotransferase and inhibits aspartate ammonia-lyase by competing with aspartate (Ki/Km 0.23). The fumarate analogue (E)-3-arsonoacrylic acid and the malate analogue (RS)-3-arsonolactate also inhibit fumarate hydratase, competing with fumarate (Ki/Km 1.8) and malate (Ki/Km 1.6) respectively. Attempted non-enzymic transamination of 3-arsonoalanine gave elimination of arsenite, in contrast with the transamination of 3-phosphonoalanine, which is either successful or leads to loss of phosphate.