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At least 19 recordsLinked to original sources

PubMed2025

Deazapurine Amide-Bond Synthetases: a New Family of Amide-Bond-Forming Enzymes Driving the Diversity of Peptidyl Deazapurine Natural Products.

Amide bond-forming enzymes play a crucial role in generating structural diversity in natural products by assembling them from relatively simple precursors. Two distinct types of standalone amid-bond-forming enzymes are commonly involved in natural product biosynthesis, including ATP-grasp enzymes and amide bond synthetases. Here, we report a new family of amide bond synthetases that catalyze amide bond formation between deazapurine as the sole carboxylic acid substrate and various amine substrates, which we have designated as deazapurine amide bond synthetases (DABS). This evolutionarily related enzyme family plays a central role in diversifying the structures of peptidyl deazapurine natural products. Our gene mining analysis reveals that most DABS-associated biosynthetic gene clusters (BGCs) remain cryptic. Therefore, systematic characterization of these cryptic BGCs holds great potential for discovering novel peptidyl deazapurine natural products with diverse biological activities.

Biological Products↗

PubMed1978

The effects of replacing ester by amide on the biological properties of compounds related to acetylcholine.

1 Replacement of ester by amine in series of derivatives of diphenylacetic acid reduces the affinity for muscarine-sensitive acetylcholine receptors of the guinea-pig ileum from 40- to 100-fold. With similar series of phenylacetic acid the reduction is only 2- to 4-fold. In both series changes in the composition of the onium group produce similar changes in the affinity of amides and esters and it appears that the stiffness of the amide bond reduces the binding of the phenyl groups at the far end of the molecule from the onium atom. 2 Replacement of ester by amide in similar series of acetyl compounds reduces activity on the guinea-pig ileum over 1000-fold and on the frog rectus over 50-fold. Compounds with larger onium groups are antagonists on both preparations with log affinity constant around 3. The amides have similar affinity for electric eel acetylcholinesterase. 3 The amides are slightly bigger than the esters in solution and slightly more hydrophilic. 4 Replacement of ester by amide in acetylcholine reduces the proportion of gauche conformer about the C--C--bond from 100% to 39%. 5 The ability of acetylcholine to activate receptors is thought to depend on some degree of flexibility in the --CO--0--bond, though the hydration of the bond may also be important.

Acetylcholine↗

PubMed1976

Incorporation of intravenously administered urea-15N into sheep plasma proteins and their amide groups.

Two sheep with a low and high nitrogen intake (7.6 and 24 g N/day respectively) were given a single intravenous dose of 15N-labelled urea (15.3 mg 15N/kg b.w.) The findings were as follows. The greater part of non-retained 15N from the administered dose was excreted during the first day after the intravenous administration of 15N-urea. Daily excretion in the faeces amounted to 1.35-2.37% of the 15N in the given dose. With a low N intake, more 15N from the given dose (59.4%) was retained in the N pool than with a high N intake (50.5%). The net passage of 15N into the rumen and 15N incorporation into the amide-N of the plasma proteins was likewise greater. 15N incorporation into the amide-N of the plasma proteins rose steadily for 3 days. The porportion of amidic 15N in the plasma proteins rose steadily for 3 days. The proportion of amidic 15N in the plasma protein total 15N changed on the second and third day after administering 15N-urea from 8% to 16%, with the maximum at the beginning of the second day. The amount of 15N incorporated into the proteins in 1 litre plasma attained up to 3% of the given dose. It is concluded from the results that the synthesis of amino acids and their amide groups is both a quantitatively and a qualitatively important metabolic route for the reutilization of blood urea nitrogen for protein synthesis in ruminants.

Amides↗

PubMed1979

Solubility in amide-water cosolvent systems II: Cosolvent excess at solute surface.

The solubility of methylparaben was determined at 25 degrees in a series of amide-water cosolvent systems. The data were used to demonstrate the possibility of an amide excess at or near the ester solute over that in the bulk solvent. The analysis, stemming from an interfacial tension-solute area solubility model proposed by earlier workers, involved data obtained as a function of amide concentration and as a function of amide alkylation. Both sets of data support the basic contention of the paper.

Amides↗

PubMed1979

Do cleavages of amides by serine proteases occur through a stepwise pathway involving tetrahedral intermediates?

The mechanism of the serine protease-catalyzed cleavage of amides (acylation) was examined in terms of the basicity of the functional groups participating in the catalysis. It is proposed that the reaction does not proceed through a stepwise pathway, as opposed to the cleavage of esters and anilides, which start with general base-catalyzed formation of the tetrahedral intermediate followed by its general acid-catalyzed breakdown. Instead, the proton abstracted from the hydroxyl group of the serine by the imidazolyl group of the histidine is donated to the nitrogen atom of the leaving group of the amide before the bond between the carbonyl carbon atom of the amide and the attacking serine oxygen atom is completed. Reactions proceed by a SN2-like reaction through the cooperation of acid catalysis by the imidazolyl cation and nucleophilic attack by the serine. The mechanisms of the enzymatic hydrolyses of anilides and esters proceed through a discrete tetrahedral intermediate, but the enzymatic hydrolyses of amides probably do not.

Amides↗

PubMed1978

E.s.r. study of spin-trapped radicals formed during the photolysis of aqueous solutions of acid amides and H2O2.

Free radicals formed by the reactions of OH radicals with amides and their N-methylated derivatives in aqueous solutions have been studied. The OH radicals were produced by U.V.-photolysis of H2O2, and the short-lived amide radicals were converted to more stable nitroxide radicals by addition to a spin-trap, tert-nitrosobutane. The spin-trapped radicals were identified by e.s.r. spectroscopy. For acetamide, chloroacetamide, malonamide, succinamide and propionamide, the observed radicals were formed by H-abstraction from the carbon atoms attached to the carbonyl group. The H atom attached to the carbonyl group was abstracted in formamide. For N-methyl acetamide, N,N-dimethyl acetamide and the corresponding formamide derivatives, H-abstraction occurred only from the N-methyl group. The non-equivalency of the amide protons was observed in the spin-trapped radicals for acetamide, formamide, malonamide, succinamide and propionamide. The identification of the site of OH attack on N-methyl amides is helpful for the study of radical formation in peptides and proteins.

Acetamides↗

PubMed1979

Analyses of infrared amide bands of chitin.

Infrared spectra of chitin isolated from various biological species were measured by Fourier transform technique. The recorded spectra were decomposed into component bands within 1500--1750 cm-1 and 3000--3500 cm-1 spectral regions; it allowed us to establish the precise position of amide I and amids II bands. It was shown that the positions of amide I and amide II bands are independent of the source from which chitin was isolated.

Amides↗

PubMed1979

Characteristics of lithium iodide-containing poly(ethylene glycol) as a gas chromatographic stationary phase, and its application to analysis of amidic drugs.

The characteristics of lithium iodide-containing poly(ethylene glycol) as a gas chromatographic stationary phase have been evaluated in terms of partial free energy of transfer (delta G t0) from poly(ethylene glycol) to the lithium iodide-poly(ethylene glycol) system for a variaty of amides (n-fatty acid amides, lactams, benzamides, anilides, nicotinamides, isonicotinamides, barbiturates, pyrazolones) and several amines. The changes in relative retention and resolution of two solute peaks caused by the addition of lithium iodide to poly)ethylene glycol) are correlated with the difference in their delta Gt0 values. The application to the specific separation of some amidic drugs is demonstrated.

Amides↗

PubMed1978

Free radicals in U.V.-irradiated aqueous solutions of substituted amides: an e.s.r. and spin-trapping study.

The radicals produced by reactions of hydroxyl radicals with alkyl substituted ureas and amides in aqueous solutions have been investigated. Hydroxyl radicals were produced by U.V. photolysis of H2O2 and the short-lived amide and urea radicals were spin-trapped by t-nitrosobutane and identified by e.s.r. For all N-alkyl derivatives of urea and acetamide, and for N,N-dimethyl propionamide and N,N-diethyl formamide, only radicals centred on N-alkyl groups were detected. Radicals situated only on alkyl groups attached to the carbonyl carbon were observed for dimethyl acetamide, trimethyl acetamide and butyramide. However, for N,N-dimethyl butyramide, N, N-diethyl butyramide, N-methyl propionamide and N, N-diethyl propionamide, free radicals were formed which were localized on the alkyl group attached to the amide carbon as well as those attached to nitrogen. The hydrogen atom bound to the carbonyl carbon was abstracted in N-ethyl formamide. Acyl radicals formed by C-N scission due to direct U.V. photolysis of N, N-dimethyl butyramide and N,N-dimethyl propionamide were also detected.

Acetamides↗

PubMed1978

Specific modification of the properties of the N-hydroxylase. Relationship with carcinogenesis by aromatic amides.

N-hydroxylation represents the first and limiting step in the metabolic pathway leading to the carcinogenic activity of aromatic amines and amides. Using a method recently developed by the same authors (Analytical Biochemistry, in press), the effects of pretreatment of male adult rats with N-2-acetylaminofluorene (2AAF), N-4-acetylaminofluorene (4AAF), N-4-acetyl-aminobiphenyl, (4-AABP), and phenobarbital (PB), on the kinetic parameters of the N-hydroxylase activity have been evaluated and compared. Our resutls clearly demonstrate that both hepatocarcinogenic amides, 2-AAF and 4-AABP very significantly increase the affinity of the activating enzyme towards both substrates; on the other hand, 4-AAF and PB, which are non-carcinogenic compounds slightly decrease the affinity of the enzyme. In conclusion, the carcinogenic aromatic amides seem to specifically modify the catalytic properties of the enzyme responsible for their own metabolic activation.

2-Acetylaminofluorene↗

PubMed1979

Amide hydrogen exchange rates of peptides in H2O solution by 1H nuclear magnetic resonance transfer of solvent saturation method. Conformations of oxytocin and lysine vasopressin in aqueous solution.

The NH exchange rates in aqueous media of oxytocin and 8-lysine vasopressin (LVP) have been measured by using transfer of solvent saturation method. The data are consistent with a "highly motile" dynamic equilibrium between folded and highly solvated conformations. The highly-motility limit applies to the exchange of NH hydrogens of oxytocin and LVP. Folded structures are more prevalent in oxytocin than in LVP. Partial shielding is indicated for peptide hydrogens of Asn5 and perhaps also Cys6 of oxytocin and for Cys6 of LVP. It is tentatively proposed that the folded conformation of oxytocin in aqueous media may contain a parallel beta-structure in the tocinamide ring consisting of two hydrogen bonds: one between the Tyr2 C = O and Asn5 peptide NH as originally proposed for the preferred conformation of oxytocin in dimethyl sulfoxide (D. W. Urry and R. Walter), and the second between he Cys1 C = O and the Cys6 NH. In LVP the hydrogen bond between the Tyr2 C = O and Asn5 peptide NH appears to be absent. The acylic tripeptide sequences (-Pro-X-Gly-NH2) of both hormones appear to be predominantly solvated. The second-order rate constants for acid catalyzed exchange of the primary amide hydrogens of Gln4, Asn5, and Gly9 of oxytocin are consistently greater for the trans NH than for the corresponding cis NH. This observation can be rationalized in terms of mechanisms involving protonation of either the amide oxygen, or the amide nitrogen, but with limited rotation about the C - N bond.

Lypressin↗

PubMed1976

[Effect of prajmalium bitartrate and procaine amide on ventricular extrasystoles (author's transl)].

Prajmalium bitartrate (Neo-Gilurytmal) was given to 19 patients, who had either runs of ventricular extrasystoles or frequent extrasystoles. The E. C. G. was continuously monitored on magnetic tape. At a dosage of 80 mg/d (20 mg every six hours) a significant reduction in ventricular extrasystoles was demonstrated on 20 separate occasions. After two hours extrasystoles decreased to 63% of the initial level. After six hours practically the full effect of the drug had been reached; the reduction in extrasystoles stabilized after 12 hours at an average of 30% of initial level. Ten hours after the last tablet had been taken the frequency of extrasystoles had risen to 57% of initial level. Comparison with procaine amide (3 g/d) in 14 patients revealed no significant difference between the two drugs. Prajmalium bitartrate was well tolerated, while three patients receiving procaine amide complained of nausea and gastrointestinal symptoms, so that treatment had to be discontinued in two. In one patient, receiving procaine amide by continuous drip, there were reversible joint pains, resembling lupus erythematodes.

Adult↗

PubMed1975

Subcellular and functional effects of quinidine, procaine amide, and lidocaine on rat myocardium.

Different antiarrhythmic agents such as quinidine, procaine amide, and lodocaine at 1 mM concentrations were found to depress the ability of an isolated perfused rat heart to generate contractile force. Quinidine, but not procaine amide or lidocaine, decreased calcium uptake by both mitochondrial and microsomal fractions at different concentrations of calcium. The mitochondrial phosphorylation rate, respiratory control index, and state 3 oxygen consumption, but not ADP:O ratio and state 4 oxygen consumption, were depressed by only quinidine. None of these agents had any effect on myofibrillar Mg2+-ATPase or Ca2+-stimulated ATPase activities. On the other hand, sarcolemmal Mg2+-ATPase and Ca2+-ATPase activities, but not Na+-K+-ATPase activity, were increased by all these drugs. The sarcolemmal adenylate cyclase (EC 4.6.1.1) activity was decreased by quinidine only. These results suggest some similarities and differences in the sites of action of quinidine, procaine amide, and lidocaine within the myocardium.

Adenosine Triphosphatases↗

PubMed1977

Damage and repair of DNA in cultured mammalian cells with N-diazoacetylglycine amide.

N-Diazoacetylglycine amide, a diazochetoalkane, has been studied in vitro for DNA damage and repair in cells of a cloned subline from a BALB/c mouse. To our present knowledge, none of these compounds have been investigated for such activities. At nontoxic levels, a prolonged dose-dependent unscheduled DNA synthesis was observed by autoradiography. DNA damage was studied by sedimentation through alkaline sucrose gradients after the cells were lysed on the gradients. Treatment of the cells for 1 hr with nontoxic doses of N-diazoacetylglycine amide resulted in slower sedimentation of DNA. The number of single-strand breaks appeared rather linearly dose dependent for a large range of concentrations. Breaks were at their maximum after 1 hr of treatment, and no further increase in the number of breaks was seen. Some repair of the breaks probably occurs, but repair was sluggish even 68 hr after treatment. A significant part of the breaks was observed after incubation at 4 degrees in an ethylenediaminetetraacetate hypotonic solution. This seems to indicate that the compound does not require metabolic activation. Nontoxic doses of N-diazoacetylglycine amide and other similar derivatives exert mutagenic and carcinogenic activities. The presence of DNA damage and the difficulty in its repair at such doses could be related to both of these biological properties.

Azo Compounds↗

PubMed1979

Individual assignments of amide proton resonances in the proton NMR spectrum of the basic pancreatic trypsin inhibitor.

Studies of proton-proton nuclear Overhauser effects were used to obtain individual assignments of 17 amide proton resonances in the 360 MHz proton nuclear magnetic resonance spectrum of the basic pancreatic trypsin inhibitor. First, optimizing the conditions for obtaining selective nuclear Overhauser effects in the presence of spin diffusion in macromolecules is discussed. Truncated driven nuclear Overhauser experiments were used to assing the amide proton resonances of the beta-sheet in the inhibitor. It is suggested that these techniques could serve quite generally to obtain individual resonance assignments in beta-sheet secondary structures of proteins. Combination of nuclear Overhauser studies with spin decoupling further resulted in individual assignments of the gamma-methyl resonances of the two isoleucines and numerous Calpha and Cbeta protons.

Amides↗

PubMed1977

Lipopeptidophosphoglycan from Trypanosoma cruzi. Amide and ester-linked fatty acids.

Lipopeptidophosphoglycan, extracted from whole cells of epimastigote forms of Trypanosoma cruzi, has now been shown to contain 12.6% of fatty acids in addition to the previously identified content of neutral sugars (60%), glucosamine (0.8%), peptide (9.5%) and acid-hydrolyzable phosphate (2%). The main fatty acids are palmitic (6.9%) and lignoceric (4.6%) acids. Stearic (0.55%), oleic (0.15%) and myristic (0.18%) acids were also found. One third of the fatty acids are bound in the lipopeptidophosphoglycan as esters (14 mmol%) and two thirds as amides (28 mmol%). Lignoceric acid was found to be bound only as amide. Two ninhydrin-positive compounds, obtained by chloroform extraction of a total acid hydrolysate of the lipopeptidophosphoglycan, were tentatively identified as sphingosine bases.

Amides↗

PubMed1979

[Metabolism of dicarboxylic amino acids and their amides in bacteria of the genus Citrobacter].

In 58 Citrobacter strains the pathways of the utilization of dicarbonic amino acids and their amides were studied. These organisms were found to be incapable of decarboxylating glutaminic and asparaginic acids, as well as their amides. All the strains could actively desamidizate asparagine. Not all of these strains showed glutaminase activity. Aspartate-aminotransferase occurred twice as often as alanine-aminotransferase, the level of activity being approximately the same. The Citrobacter strains desamidizated asparaginic acid with great constancy, but only in 1/3 of them this reaction occurred via an aspartase route. The desamidization of asparaginic acid in Citrobacter seemed to proceed in different ways. The desamidization of glutaminic acid was observed only in a part of the strains, and the reaction proceeded less actively.

Amides↗

PubMedDate not supplied

[Protein amidation in the aging organism].

The role of protein amide groups was studied in the process of the organism ageing. It is shown that with ageing there occurs the asparagin deamidation in water-soluble and water-insolbule proteins of the rat brain, liver and heart. The glutamine content in the old rat tissues remains at the level determined in the young animal tissues. Tissue proteins of old rats are better substrates for protein--a complex of proteinases of a wide specificity that those of young animals. An increased attack of the old animals proteins by nonspecific proteinases is due to a decrease in their amidation degree during ageing.

Aging↗