Showing papers on "Decarboxylation published in 1983"

New and improved methods for the radical decarboxylation of acids

Abstract: Carboxylic acid esters derived from N-hydroxypyridine-2-thione undergo efficient radical chain decarboxylation to the corresponding nor-alkane on treatment with either tri-n-butylstannane or t-butylmercaptan; in the absence of these hydrogen atom donors a smooth decarboxylative rearrangement giving noralkyl 2-pyridyl sulphides is observed.

Purification, characterisation and reconstitution of glutaconyl-CoA decarboxylase, a biotin-dependent sodium pump from anaerobic bacteria

Abstract: 1 Glutaconyl-CoA decarboxylase from Acidaminococcus fermentans is a biotin enzyme, which is integrated into membranes. It is activated by Triton X-100 and inhibited by avidin. The results obtained by a combination of both agents indicate that biotin and the substrate-binding site are located on the same side of the membrane. 2 The decarboxylase was solubilized with Triton X-100 and purified by affinity chromatography on monomeric avidin-Sepharose. The enzyme is composed of three types of polypeptides: the group of α chains (Mr 120000–140000) containing the biotin, the β chain (60000) and an apparently hydrophobic γ chain (35000). Sodium ions specifically protected the latter chain from tryptic digestion. It was supposed, therefore, that this chain might function as the Na+ channel. The β and γ chains but not the α chain could be labelled by N-ethyl-[14C]maleimide. Similar decarboxylases but with much smaller biotin peptides (Mr 15000–20000) were isolated from Peptococcus aerogenes and Clostridium symbiosum. 3 The decarboxylases from all three organisms could be reconstituted to active sodium pumps by incubation with phospholipid vesicles and octylglucoside followed by dilution. The Na+ uptake catalysed by the enzyme from A. fermentans was completely inhibited by monensin and activated twofold by valinomycin/K+ indicating an electrogenic Na+ pump. The coupling between Na+ transport and decarboxylation was not tight. During the reaction the ratio decreased from initially 1 to 0.2. 4 The three organisms mentioned above and Clostridium tetanomorphum without glutaconyl-CoA decarboxylase are able to ferment glutamate and require 10 mM Na+ for rapid growth. There is no correlation between the concentration of monensin necessary to inhibit growth and the presence of decarboxylase in these organisms.

Subunit composition of oxaloacetate decarboxylase and characterization of the α chain as carboxyltransferase

Abstract: Oxaloacetate decarboxylase from Klebsiella aerogenes was shown to be composed of three different subunits alpha, beta, gamma with Mr 65 000, 34 000 and 12 000, respectively. On dodecylsulfate/polyacrylamide gels the smallest of these subunits was heavily stained with silver but poorly with Coomassie brilliant blue. All three subunits were resolved and clearly detectable by high-performance liquid chromatography in a dodecylsulfate-containing buffer. Biotin was localized exclusively in the alpha chain. Freezing and thawing of the isolated membranes in the presence of 1 M LiCl released the alpha chain which was subsequently purified to near homogeniety by affinity chromatography on monomeric avidin-Sepharose. No beta or gamma chain were detectable in this alpha chain preparation and no oxaloacetate decarboxylation was catalyzed. The isolated alpha chain, however, was a catalytically active carboxyltransferase as evidenced from the isotopic exchange between [1-14C]pyruvate and oxaloacetate. The rate of this exchange reaction was about 9 U/mg protein and was completely independent of the presence of Na+ ions. The ease with which the alpha chain was released from the membrane characterize this subunit as a peripheral membrane protein. The beta and gamma chain, on the other hand, stick so firmly in the membrane that they are only released by detergents, thus indicating that these are integral membrane proteins. Limited tryptic digestion of oxaloacetate decarboxylase led to a rapid cleavage of the alpha chain, yielding a polypeptide of Mr 51 000 which was devoid of biotin. Degradation of the beta chain required prolonged incubation periods and was markedly influenced by Na+ ions which had a protective effect against proteolysis. A proton is required in the decarboxylation of oxaloacetate and CO2 arises as primary product. The other alternative, i.e. generation of HCO3- with H2O as substrate, has been excluded.

Purification and characterization of bovine hepatic uroporphyrinogen decarboxylase.

Abstract: Uroporphyrinogen decarboxylase (EC 4.1.1.37) has been purified to homogeneity from bovine liver by using isoelectric and salt precipitations, followed by chromatography on DEAE-cellulose, phenyl-Sepharose, hydroxylapatite, and Sephacryl S-200. The purified enzyme is a monomer with an Mr approximately 57 000 and an isoelectric point at pH 4.6. Enzyme activity is optimal in buffers having an ionic strength of approximately 0.1 M and a pH of 6.8. The purified enzyme has a specific activity (expressed as the disappearance of uroporphyrinogen I) of 936 nmol X h-1 X (mg of protein)-1. The purified enzyme catalyzes all four decarboxylation reactions in the conversion of uroporphyrinogen I or III to the corresponding coproporphyrinogen. The rate-limiting step in the physiologically significant conversion of uroporphyrinogen III to coproporphyrinogen III is the decarboxylation of heptacarboxylate III. Kinetic data suggest that the enzyme has at least two noninteracting active sites. At least one sulfhydryl group is required for catalytic activity. The enzyme is inhibited by sulfhydryl-specific reagents and by divalent metal ions including Fe2+, Co2+, Cu2+, Zn2+, and Pb2+. The pattern of accumulation of intermediate (hepta-, hexa-, and pentacarboxylate porphyrinogens) and final (coproporphyrinogen) decarboxylation products is affected by the ratio of substrate (uroporphyrinogen I or III) concentration to enzyme concentration. Under physiologic conditions where the uroporphyrinogen to enzyme ratio is low, the substrate is nearly quantitatively decarboxylated, and the major product is coproporphyrinogen. If the ratio of uroporphyrinogen to enzyme is high, intermediates accumulate, and heptacarboxylate porphyrinogen becomes the major decarboxylation product.(ABSTRACT TRUNCATED AT 250 WORDS)

The generation of hydroxyl and alkoxyl radicals from the interaction of ferrous bipyridyl with peroxides.

Abstract: Reaction conditions by which the iron-chelate ferrous bipyridyl can be used as a Fenton reagent to generate specifically alkoxyl radical (OR) from its corresponding alkyl hydroperoxide (ROOH) without producing hydroxyl radical (OH) as a result of autoxidation are described In this manner, the relative ability of common OH-scavenging agents to react with OH and various OR species could be assessed When OH was generated from H2O2, 4-methylmercapto-2-oxobutyrate, ethanol and benzoate all were oxidized When OR (cumoxyl radical, t-butoxyl radical or ethoxyl radical) was generated specifically, each was found to oxidize 4-methylmercapto-2-oxobutyrate and ethanol In contrast with OH, however, none of the OR radicals mediated the decarboxylation of benzoate Cross-competition studies with the scavengers showed that, in contrast with the OH-dependent reaction, the OR-dependent oxidation of 4-methylmercapto-2-oxobutyrate and ethanol was not inhibited by benzoate Rate constants for ferrous bipyridyl oxidation by ROOH and by H2O2 were found to be essentially the same, and therefore the differential oxidation of the various scavengers was not a reflection of iron-peroxide interaction, but rather an interaction between generated oxy radicals and the scavengers In contrast with the H2O2 system, catalase did not inhibit the oxidation of 4-methylmercapto-2-oxobutyrate or ethanol by either the cumene hydroperoxide or the t-butyl hydroperoxide system, suggesting that the oxidizing species was not derived from H2O2 These results suggest that benzoate decarboxylation might serve as a more specific probe to detect the presence of OH than either 4-methylmercapto-2-oxobutyrate or ethanol, which react readily with OR

The biosynthesis of p-tyramine, m-tyramine, and β-phenylethylamine by rat striatal slices

Abstract: Slices of striatal tissue obtained from saline-injected rats were incubated with 3H-phenylalanine in the presence of pargyline. This resulted in the formation of 3H-m-tyramine, 3H-p-tyramine, and 3H-phenylethylamine. Pretreatment of the rats with alpha-methyl-p-tyrosine reduced the formation of 3H-m-tyramine and 3H-p-tyramine, but enhanced the formation of 3H-phenylethylamine. After incubation of striatal tissue obtained from saline-injected rats with 3H-ptyrosine, only 3H-p-tyramine was produced. In this case, alpha-methyl-p-tyrosine pretreatment enhanced 3H-p-tyramine formation. Striatal slices incubated with 3H-m-tyramine or 3H-p-tyramine did not yield any significant quantity of 3H-phenylethylamine; nor was 14C-phenylethylamine converted to 14C-m-tyramine or 14C-p-tyramine. Pretreatment of the rats with the monoamine oxidase inhibitor pargyline did not appreciably affect these findings. After incubation with 3H-dopamine very small quantities of 3H-m-tyramine and 3H-p-tyramine were formed, the ratio between them being 7:1. It is concluded that the major biosynthetic route for m-tyramine formation in the rat striatum is by hydroxylation of phenylalanine, probably by tyrosine hydroxylase to m-tyrosine, followed by decarboxylation, probably by L-aromatic amino acid decarboxylase, to m-tyramine. para-Tyramine is formed by decarboxylation of p-tyrosine, and phenylethylamine similarly by decarboxylation of phenylalanine.

Thermal aging study of carboxyl‐terminated polybutadiene and poly(butadiene‐acrylonitrile)‐reactive liquid polymers

Abstract: A thermal aging study of carboxyl-terminated polybutadiene (CTB) and poly(butadiene-acrylonitrile) (CTBN) reactive liquid polymers has been conducted at 50°, 75°, 100°, and 125°C. All CTB and CTBNs are stable at 50°C aging. On aging at higher temperatures prior to use, viscosities of CTB and CTBNs increase, and terminal carboxylic acid functional groups start disappearing. Rate of viscosity increase and rate of carboxylic acid functional group disappearance increase with higher aging temperature and also with higher cyano group concentration in the polymers. The major cause of rapid viscosity increase and disappearance of carboxylic acid functional groups seems to be crosslinking between terminal carboxylic acid groups and cyano groups, which form imide structures. Crosslinking among the unsaturation in polybutadiene segments may contribute to the slow, steady viscosity increase. No acid-anhydride formation and decarboxylation reaction, which may also result in viscosity increase and disappearance of carboxylic acid functional groups, are observed during the thermal aging at elevated temperatures.

Tricarboxylic Acid Cycle Activity in Relation to Itaconic Acid Biosynthesis by Aspergillus terreus

Abstract: Summary: Cell-free extracts of an itaconic acid producing strain of Aspergillus terreus contained NADP-dependent isocitrate dehydrogenase activity but no NAD-dependent activity was detected. During the acid-producing phase the activity of the NADP-linked enzyme fell to one-eighth of its value during the growth phase, whereas citrate synthase activity increased. Intact mitochondria were isolated from growth and production phase mycelium. The preparation from the growth phase oxidized exogenous NADH and all tricarboxylic acid cycle intermediates tested. That from the production phase oxidized tricarboxylic acid cycle intermediates at a reduced rate but exogenous NADH oxidation remained high. [2-14C]Acetate was incorporated into itaconic acid and over 90% of the incorporated radioactivity was located in the methylene carbon. [1-14C]-Acetate was a poorer precursor and did not preferentially label the methylene carbon. These results support the view that itaconic acid biosynthesis in A. terreus occurs by decarboxylation of aconitic acid, the latter produced by the normal reactions of the tricarboxylic acid cycle.

Pathway of Gallic Acid Biosynthesis and Its Esterification with Catechins in Young Tea Shoots

Abstract: Shikimic acid-G-14C, phenylalanine-U-14C, and trans-cinnamic acid-3-14C were incorporated into the gallic acid moiety of (—)-epicatechin-3-gallate and (—)-epigallocatechin-3-gallate in young tea shoots. The incorporation of shikimic acid-7-14C into the gallic acid was almost equal to that of shikimic acid-G-14C, i.e. decarboxylation of the side chain did not occur during the conversion of shikimic acid to gallic acid and the conversion apparently was due to dehydrogenation of the shikimic acid. These results suggest at least two pathways for gallic acid biosynthesis in tea shoots; a) a pathway through phenylpropanoid, and b) a pathway through the dehydrogenation of shikimic acid.Esterification of gallic acid with catechins was also confirmed by tracer experiments in young tea shoots.

Photoelectrochemistry of levulinic acid on undoped platinized n-titanium dioxide powders

Abstract: The photoelectrochemistry of levulinic (4-oxopentanoic) acid, the major product of controlled degradation of cellulose by acids, has been investigated. Since this acid can be present in waste streams of biomass processing, we investigated the photoelectrochemical reactions of this acid on slurries composed of semiconductor/metal particles. The semiconductor investigated was platinized undoped n-TiO/sub 2/, as anatase, anatase-rutile mixture, or rutile. The effects of the level of platinization, pH, acid concentration, and the semiconductor surface area were investigated. In addition to the decarboxylation reaction leading to methyl ethyl ketone, we have also observed novel cleavages of the C-C backbone leading to propionic acid, acetic acid, acetone, and acetaldehyde as major products. These lower molecular weight carboxylic acids undergo decarboxylation at the slurry diodes to ethane and methane. The organic product distribution is a complex function of the crystallographic phase of n-TiO/sub 2/ and of the level of metallization of the semiconductor powder. 2 figures, 1 table.

Persulfate/silver ion decarboxylation of carboxylic acids. Preparation of alkanes, alkenes, and alcohols

Abstract: Etude de la decarboxylation d'acides alcanoiques, cyclohexanecarboxylique, adamantanecarboxylique-1 et norbornanecarboxylique-2 en presence de Ag(II) dans (eau/acetonitrile) et en presence d'un cocatalyseur Cu(II)

Bacterial Decarboxylation of o-Phthalic Acids.

Abstract: The decarboxylation of phthalic acids was studied with Bacillus sp. strain FO, a marine mixed culture ON-7, and Pseudomonas testosteroni. The mixed culture ON-7, when grown anaerobically on phthalate but incubated aerobically with chloramphenicol, quantitatively converted phthalic acid to benzoic acid. Substituted phthalic acids were also decarboxylated: 4,5-dihydroxyphthalic acid to protocatechuic acid; 4-hydroxyphthalic and 4-chlorophthalic acids to 3-hydroxybenzoic and 3-chlorobenzoic acids, respectively; and 3-fluorophthalic acid to 2-and 3-fluorobenzoic acids. Bacillus sp. strain FO gave similar results except that 4,5-dihydroxyphthalic acid was not metabolized, and both 3- and 4-hydroxybenzoic acids were produced from 4-hydroxyphthalic acid. P. testosteroni decarboxylated 4-hydroxyphthalate (to 3-hydroxybenzoate) and 4,5-dihydroxyphthalate but not phthalic acid and halogenated phthalates. Thus, P. testosteroni and the mixed culture ON-7 possessed 4,5-dihydroxyphthalic acid decarboxylase, previously described in P. testosteroni, that metabolized 4,5-dihydroxyphthalic acid and specifically decarboxylated 4-hydroxyphthalic acid to 3-hydroxybenzoic acid. The mixed culture ON-7 and Bacillus sp. strain FO also possessed a novel decarboxylase that metabolized phthalic acid and halogenated phthalates, but not 4,5-dihydroxyphthalate, and randomly decarboxylated 4-hydroxyphthalic acid. The decarboxylation of phthalic acid is suggested to involve an initial reduction to 1,2-dihydrophthalic acid followed by oxidative decarboxylation to benzoic acid.

7-Substituted benzo[b]thiophenes and 1,2-benzisothiazoles. Part 1. Hydroxy- or methoxy-derivatives

Abstract: Readily available 2-hydroxy-3-methoxybenzaldehyde (orthovanillin) is converted, via thermal rearrangement (Newman–Kwart) of the O-aryl-NNdimethylthiocarbamate, into 2-mercapto-3-methoxybenzaldehyde (3). This thiol undergoes base-catalysed condensation with compounds of the type ClCH2X (e.g. X = CO2H, Ac, or CN), to give the appropriate 2-(X-substituted)-7-methoxybenzo[b]thiophene. Successive demethylation and decarboxylation of 7-methoxybenzo[b]thiophene-2-carboxylic acid provides a convenient route to 7-hydroxybenzo[b]thiophene. 7-Methoxybenzo[b]thiophene undergoes bromination and nitration at the 4-position; the structure of the 4-bromo compound is confirmed by an unambiguous synthesis. 2-Mercapto-3-methoxybenzaldehyde (3) reacts with chloramine to provide a simple synthesis of 7-methoxy-1,2-benzisothiazole. 2-Mercapto-3-methoxybenzonitrile, obtained as above from the corresponding 2-hydroxy compound, gives 2-acetyl-3-amino-7-methoxybenzo[b]thiophene when treated with chloropropanone, and 3-amino-7-methoxy-1,2-benzisothiazole when treated with chloramine.

Catalysis by solid superacids. 18. Nafion-H perfluorinated resin sulfonic acid promoted deacetylation and decarboxylation of aromatics

Abstract: Desacetylation, d'(acetyl polymethyl)-, (diacetyl tetramethyl) benzenes et acetyl-9 anthracene et etude de la decarboxylation d'acides polymethyl-benzoiques et anthroique-9

Photofragmentation of acrylic acid and methacrylic acid in the gas phase

Abstract: Decarboxylation des acides acrylique (193 mm) et methacrylique (249 mm) Formation de CO 2 et de carbene Processus photophysique se manifestant prealablement a la reaction chimique

Preparation of all the possible ring-deuteriated benzoic acids by reductive dehalogenation of the corresponding halogenobenzoic acids with raney alloys in an alkaline deuterium oxide solution

Abstract: All the possible undeuteriated benzoic acids were prepared mainly by treatment of the corresponding bromobenzoic acid with Raney Cu–Al alloy in 10% NaOD–D2O solution. [2,3,4,5,6-2H5] Benzoic acid was obtained from pentafluorobenzoic acid by a similar reaction. However, only [2,3,4,5-2H4] benzoic acid was prepared by decarboxylation of [2,3,4,5-2H4] phthalic acid.