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PubMed1975

The S-n-propyl analogue of S-adenosylmethionine.

A special strain of Saccharomyces cerevisiae responded to a supplement of S-n-propyl-L-homocysteine in the culture medium by synthesizing S-adenosyl-(S-n-propyl)L-homocysteine, the S-n-propyl analogue of S-adenosylmethionine. S-n-Butyl-L-homocysteine reacted sparingly with this strain, but S-isopropyl-L-homocysteine failed to form detectable quantities of the corresponding S-adenosylsulfonium compound. The S-n-propyl compound was isolated by extraction of the cells, followed by ion-exchange chromatography, which separated it from endogenous S-adenosylmethionine. The structure was determined by hydrolytic procedures leading to overlapping fragments of known structure, 5'-n-propylthioadenosine and S-n-propyl-L-homocysteine. The new sulfonium compound was examined for its activity as n-propyl donor by substituting it for S-adenosylmethionine in methyltransferase systems. Enzymatic transpropylation was observed with S-adenosylmethionine : L-homocysteine S-methyltransferase (EC 2.1.1.10). Its rate was low in the S-adenosylmethionine : N-acetylserotonin O-methyltransferase system (EC 2.1.1.4), and below recognition with S-adenosylmethionine : guanidinoacetate methyltransferase (EC 2.1.1.2) and S-adenosylmethionine : histamine N-methyltransferase (EC 2.1.1.8).

Acetates↗
PubMed2001

High reactivity of alkyl sulfides towards epoxides under conditions of collagen fixation--a convenient approach to 2-amino-4-butyrolactones.

Epoxy crosslinking agents have been investigated for use in the fabrication of bioprosthetic devices, such as heterograft heart valve prostheses. It has been generally assumed that epoxy crosslinking takes place via amino-epoxy reactions. The present study investigated the hypothesis that the reactions of methionine residues with epoxides also can occur in biomaterial crosslinking. A series of model reactions were studied in which a mono-epoxide was combined with individual alkyl sulfides. In the present studies epoxides rapidly alkylate aliphatic sulfides, including methionine derivatives, in buffered aqueous solutions at room temperature and pH close to neutral, forming sulfonium compounds, which are stable at pH 5-7 at temperatures up to 50 degrees C, except for cases in which methionine derivatives with non-protected carboxy groups are used. The rate of reaction remains practically unchanged within the range of pH from 5 to 12, whereas in strongly alkaline media the reverse reaction occurs. This discovery can provide a better understanding of processes occurring in the fixation of bioprosthetic tissues with polyepoxides. It can also develop into a site-specific method to label methionine residues in proteins. The carboxy group-containing sulfonium betaines derived from N-protected methionines undergo cyclization in unexpectedly mild conditions, which can be used as an efficient method for preparation of N-protected 2-amino-4-butyrolactones with sensitive protective groups.

4-Butyrolactone↗
PubMed1962

Utilization of S-adenosylmethionine by micro-organisms.

Shapiro, Stanley K. (Argonne National Laboratory, Argonne, Ill.). Utilization of S-adenosylmethionine by microorganisms. J. Bacteriol. 83:169-174. 1962.-Two types of mutants of Aerobacter aerogenes that utilize S-adenosylmethionine for growth are described. One type also responds to methionine, 5'methylthioadenosine, or a combination of homocysteine and S-methylmethionine. The second type of mutant responds only to S-adenosylmethionine or a combination of adenine and S-ribosylmethionine. The most common type of methionine mutant is unable to utilize S-adenosylmethionine for growth. The mutants are able to utilize the compounds that support growth as the sole source of sulfur. S-Adenosylhomocysteine is not utilized for growth by any of the mutants of A. aerogenes described here. There are no significant differences between the mutants and the wild type in the enzymatic decomposition of S-adenosylmethionine or in the activity of the homocysteine transmethylases. S-Adenosylmethionine does not replace the methionine requirement of the lactic acid bacteria, although Lactobacillus arabinosus shows half-maximal growth with the sulfonium compound and homocysteine. S-Adenosylhomocysteine is not utilized for growth by these organisms.

Adenine↗
PubMed1998

S-methyl derivatives from thiol compounds by the pyrolytic reaction with trimethylsulfonium hydroxide.

Base-catalyzed transesterification of acyl lipids with methanol in the presence of trimethylsulfonium hydroxide (TMSH) is an easy and convenient method for the preparation of fatty acid methyl esters for gas chromatography (GC) analyses. Free fatty acids are converted to fatty acid methyl esters by the pyrolytic reaction with TMSH as well. We have found that lipids and other compounds containing thiol groups are also converted easily to the corresponding methyl sulfides (methyl thioethers) by the pyrolytic reaction with TMSH occurring in the injector of the gas chromatograph. For example, alkane thiols such as dodecane thiol and octadecane thiol are converted to the corresponding alkyl methyl sulfides, whereas bis(methylthio) derivatives are formed from alpha,omega-alkane dithiols, e.g., 1,8-octanedithiol, and from 2,3-dimercaptopropan-1-ol (dimercaprol). Furthermore, 3beta-mercaptocholest-5-ene (thiocholesterol) is converted to 3-methylthiocholest-5-ene by the same reaction. The S-methylation reactions which finally lead to the corresponding methylthio derivatives of lipids and other compounds with thiol groups may be of diagnostic value for the structural analysis of such compounds by GC and GC/mass spectrometry.

Biochemistry↗
PubMed1985

Glutathione S-transferases catalyzed conjugation of 1,4-disubstituted butanes with glutathione in vitro.

Rat liver glutathione S-transferases catalyzed the conjugation of 1,4-diiodobutane with glutathione in vitro. The reaction followed saturation kinetics and was dependent on the concentration of the enzyme, substrate and glutathione in the incubation media. S-Benzylglutathione inhibited the enzymatic conversion of 1,4-diiodobutane to product. The cyclic sulfonium compound, gamma-glutamyl-beta-(S-tetrahydrothiophenium) alanyl-glycine was identified as the product of this conjugation reaction. This product was stable under physiological conditions in presence of rat liver cytosol but rapidly and quantitatively decomposed at pH greater than or equal to 12 to give tetrahydrothiophene.

Animals↗
PubMed1982

Dogger bank itch. 4. An eczema-causing sulfoxonium ion from the marine animal, Alcyonidium gelatinosum [Bryozoa].

Repeated exposure to the marine bryozoan, Alcyonidium gelatinosum, frequently provokes an eczematous allergic contact dermatitis known as the "Dogger Bank Itch". The dermatitis, representing a severe occupational disease, is especially widely distributed among trawlermen working in the Dogger Bank area in the North Sea. The allergy is shown to belong to the type of cell-mediated hypersensitivity. The hapten has been identified as the (2-hydroxyethyl)dimethylsulfoxonium ion. The isolation, structure determination and synthesis are discussed.

Bryozoa↗
PubMed2004

S-adenosylmethionine: nothing goes to waste.

S-adenosylmethionine (SAM or AdoMet) is a biological sulfonium compound known as the major biological methyl donor in reactions catalyzed by methyltransferases. SAM is also used as a source of methylene groups (in the synthesis of cyclopropyl fatty acids), amino groups (in the synthesis of 7,8-diaminoperlagonic acid, a precursor of biotin), ribosyl groups (in the synthesis of epoxyqueuosine, a modified nucleoside in tRNAs) and aminopropyl groups (in the synthesis of ethylene and polyamines). Even though the mechanism of most of these reactions has not been extensively characterized, it is likely that the chemistry at work is mainly driven by the electrophilic character of the carbon centers that are adjacent to the positively charged sulfur atom of SAM. In addition, SAM, upon one-electron reduction, is a source of 5'-deoxyadenosyl radicals, which initiate many metabolic reactions and biosynthetic pathways by hydrogen-atom abstraction. SAM presents a unique situation in which all constituent parts have a chemical use.

4-Butyrolactone↗
PubMed1976

[New studies on inhibition of tRNA N2 guanine methyltransferase by S-adenosyl-homocysteine and S-adenosyl-methionine analogs].

New structural analogs of S-adenosyl homocysteine (SAH) 1-9, 11-14, 19-21) and of S-adenosyl methionine (15-18) have been tested as inhibitors of a N-2 guanine methyltransferase extract from rabbit liver with E. coli B tRNA as substrate. The sulfonium compounds (mixture of +/- diastereoisomers) are more inhibitory than the sulfide derivatives but less inhibitory than SAH itself. The replacement of the aminoacid chain in SAH by various alphatic radicals leads to a correlation between their bulk and the size of the enzymatic site. The monosubstitution of N-6 amino group does not affect significantly the inhibitory effect, which is completely canceled by the disubstitution of N-6.

Animals↗
PubMed2002

Stabilization of S-adenosyl-L-methionine promoted by trehalose.

S-adenosyl-L-methionine (SAM), an important metabolic intermediate of mammals, is a well-known therapeutic agent. The molecule is chemically unstable, both in solution and in dry state, and forms different degradation products. Because the chemical instability represents a real problem during the preparation of therapeutic formulations, we investigated the capacity of some sugars to improve the SAM stability over time. In the present work, we demonstrated that the disaccharide trehalose exercises a protective effect towards the lyophilized SAM slackening its degradation (65% of SAM was detected after 50 days at 37 degrees C). A parallel study, performed to stabilize the SAM into lyophilized yeast cells enriched in the sulfonium compound, assessed the positive effect of trehalose also in whole cells, but in lesser measure.

Drug Stability↗
PubMed2000

Synthesis and characterisation of a new class of stable S-adenosyl-L-methionine salts.

S-adenosyl-L-methionine (SAM) is an important metabolic intermediate that serves as a donor of methyl and aminopropyl groups to a variety of acceptor molecules. The molecule in vitro is unstable both in solution and in crystalline form undergoing irreversible conversion to 5'-methyltioadenosine (MTA) and homoserine lactone. Since this form of instability seems to be prevented in the cell of the living organism by bonds with macromolecules, we designed and developed a novel class of salts of SAM with large size anions to improve the stability of the sulfonium compound outside the cell. For this purpose we synthesised and characterised by NMR and IR spectroscopy anions consisting of amidic derivatives of taurine with fatty acids. Stability studies performed with the new SAM salts indicate that SAM becomes much more stable when it interacts with large size anions and in fact, more than 84% of the SAM is recovered after 36 months in lyophilized samples. The high stability of the new products widens the possibility of new therapeutic applications of SAM in human therapy.

Anions↗
PubMed1981

Synthesis and evaluation of some stable multisubstrate adducts as inhibitors of catechol O-methyltransferase.

A new series of methylase inhibitors has been designed in which the nucleophilic methyl acceptor is attached to the adenosine and/or homocysteine fragments of the methyl donor, S-adenosylmethionine, to form a "multisubstrate adduct". In the present case, catecholamine analogues attached through a phenethyl sulfide linkage to 5'-thioadenosine or homocysteine have been synthesized, together with the corresponding methylsulfonium salts. These compounds were assayed as inhibitors of catechol O-methyltransferase, and the adenosylsulfonium salts (4) were found to be inhibitors of the enzyme.

Catechol O-Methyltransferase Inhibitors↗
PubMed1988

Dimethylsulfonium and thiolanium analogues of the muscarinic agent oxotremorine.

Dimethylsulfonium (6a and 6b) and thiolanium analogues (7a and 7b) of oxotremorine were synthesized and found to be potent muscarinic agents in vivo and vitro. Compound 6a exceeded oxotremorine in potency. Their affinities for muscarinic receptors in the guinea pig ileum and urinary bladder, estimated pharmacologically, were higher than those of the corresponding trimethylammonium (8a and 8b) and N-methylpyrrolidinium compounds (9a and 9b). However, the new compounds had lower intrinsic efficacies than their quaternary ammonium analogues. The compounds also had high affinity for central muscarinic receptors as measured by displacement of specifically bound (-)-[3H]-N-methylscopolamine from homogenates of the rat cerebral cortex. Half-maximal occupation of cortical muscarinic receptors by 6a, 6b, 7a, and 7b was achieved at concentrations of 0.8, 5.4, 0.3, and 3.3 microM, respectively. The competition curves of 6a, 6b, and 7a were adequately described by a two-site binding equation. The ratio of low- and high-affinity dissociation constants agreed with relative efficacy estimated on the ileum. The thiolanium salt 7a was a fairly potent nicotinic agent on the frog rectus abdominis.

Animals↗
PubMed1996

Evidence for the Importance of Polarizability in Biomimetic Catalysis Involving Cyclophane Receptors.

Cyclophanes 1-6 catalyze the nucleophilic dealkylation of a simple sulfonium compound by potassium iodide. The cation-pi interaction is important in substrate binding, but the primarily electrostatic nature of this effect does not explain all observations concerning catalysis. As a series of substituents are placed on the cyclophane framework, a systematic variation in catalyst effectiveness is seen, such that more polarizable substituents produce more potent catalysts. This provides support for the notion that transition states are especially polarizable, and catalysis can be enhanced by maximizing London dispersion forces. The reactions studied here are very similar to the broad class of biological methylations mediated by S-adenosylmethionine, and the biological catalysts may use forces similar to those described here.

Journal Article↗
PubMed2006

MIA-QSAR modelling of anti-HIV-1 activities of some 2-amino-6-arylsulfonylbenzonitriles and their thio and sulfinyl congeners.

A QSAR method based on MIA (multivariate image analysis) descriptors is applied to a series of 2-amino-6-arylsulfonylbenzonitriles and their thio and sulfinyl congeners, compounds with anti-HIV-1 activity. Two models were built in order to appraise the modelling capability when different drawing programs are used to create the set of molecules. Both models showed good predictive ability, with cross-validated Q2 of 0.712 and 0.624, and Q2 for an external validation set of 0.823 and 0.747. An ADME evaluation, by calculating the topological polar surface area (TPSA) and parameters derived from the rule of five, was also performed to proposed compounds in order to suggest absorption profiles for potential new drugs.

Administration, Oral↗
PubMed1993

Energy cost of proofreading in vivo: the charging of methionine tRNAs in Escherichia coli.

Previous in vitro work has shown that Escherichia coli methionyl-tRNA synthetase has a limited ability to discriminate against cognate methionine in the editing site designed for noncognate homocysteine. As a result, a small fraction of the correct product Met-tRNA is deacylated with the formation of a cyclic sulfonium compound, S-methyl-homocysteine thiolactone. This is exploited here to estimate energy costs associated with the destruction of a correct product by methionyl-tRNA synthetase in bacterial cells. In vivo measurements of S-methyl-homocysteine thiolactone indicate that in Escherichia coli 3.3 molecules of Met-tRNA are destroyed by deacylation per 10,000 molecules of Met-tRNA successfully transferring methionine to protein. This number of destroyed molecules of a correct product, Met-tRNA, is 30 times lower than the number of destroyed molecules of an incorrect product, homocysteinyl adenylate. Thus, most of the energy cost of proofreading in vivo is due to editing of the noncognate amino acid.

Energy Metabolism↗
PubMed1986

Purification and characterization of propylamine transferase from Sulfolobus solfataricus, an extreme thermophilic archaebacterium.

The enzyme propylamine transferase, catalyzing the transfer of the propylamine moiety from S-adenosyl(5')-3-methylthiopropylamine to several amine acceptors, has been purified 643-fold in 20% yield from Sulfolobus solfataricus, an extreme thermophilic archaebacterium optimally growing at 87 degrees C. The purified enzyme (specific activity 2.05 units/mg protein), is homogeneous by criteria of gel electrophoresis, gel filtration, isoelectric focusing and ultracentrifugation analysis. The molecular mass of the native enzyme was estimated to be about 110 kDa by gel permeation and ultracentrifugation analysis. The protein migrates on SDS/polyacrylamide gel electrophoresis as a single band of 35 kDa, suggesting that the enzyme is a trimer composed by identical subunits. An optimum pH of 7.5 and an acidic isoelectric point of 5.3 have been calculated. The optimum temperature was 90 degrees C and no loss of activity is observable even after exposure of the purified enzyme to 100 degrees C for 1 h. No reducing agents are required for enzymatic activity. Substrate specificity towards the amine acceptors is rather broad in that 1,3-diaminopropane (Km = 1675 microM), putrescine (Km = 3850 microM), sym-norspermidine (Km = 954 microM) and spermidine (Km = 1539 microM) are recognized as substrates. Conversely S-adenosyl(5')-3-methylthiopropylamine is the only propylamine donor (Km = 7.9 microM) and the deamination of the sulfonium compound prevents the recognition by the enzyme. The reaction is irreversible and initial-rate kinetic studies indicate that the propylamine transfer is operated through a sequential mechanism. 5'-Methylthioadenosine, a product of the reaction, acts as a powerful competitive inhibitor with a Ki of 3.7 microM. Enzyme-substrate binding sites have been investigated with the aid of several substrate analogs and products. Among the compounds assayed, 5'-methylthiotubercidin, S-adenosyl(5')-3-thiopropylamine and S-adenosyl-3-thio-1,8-diaminooctane are the most active inhibitors.

Archaea↗