N-substituted Amino Acids Research Articles

EPR and magnetic studies of copper amino carboxylates

Metal complexes of N-substituted amino acids provide simple but appropriate model compounds for the understanding of metal protein interactions. Seven complexes of copper viz. Cu(II) N-acetyl glycinate mono-hydrate, Cu(II) N-acetyl methioninate, Cu(II) N-acetyl alaninate, Cu(II) N-acetyl valinate, Cu(II) N-acetyl glutamate, Cu(II) cyanoacetate, and Cu(II) thio-dipropionate, have been investigated by EPR measurements. The spectra appear to arise from dimeric coppers ( s=1) coupled by anti-ferromagnetic exchange. The exchange coupling constant ‘2 J’ and the CuCu separation ‘r’ have been evaluated from the spectral data. Although the existence of bridged structure is confirmed, super-exchange via the ligands appears to be the dominant mechanism. All of these complexes exist as monomers in strongly coordinating solvents.

The isolation of four aminocyclohexenimines (mycosporines) and a structurally related derivative of cyclohexane-1:3-dione (gadusol) from the brine shrimp, Artemia

1. 1. Mycosporines, N-substituted amino acid derivatives of 1,5-dihydroxy-5-hydroxymethyl-2-methoxycyclohex-1-en-3-one, were isolated from dormant embryos (cysts) of Artemia. The major component in all strains was mycosporine (-Gly:-Ser). Smaller amounts of other mycosporines containing glycine and threonine, glycine and alaninol as well as glycine and aspartic acid residues were identified in cysts of a strain from Brazil. 2. 2. Free amino acids were released from mycosporines by treatment with either bromine water or an iodine peroxidase (EC 1.11.1.8). 3. 3. The amount of mycosporines in developing cysts decreased while motile nauplii contained only gadusol (1,4,5-trihydroxy-5-hydroxymethyl-2-methoxycyclohex-1-en-3-one).

Hydrolysis of choline esters of N-substituted amino acids under the action of butyrylcholinesterase

Hydrolysis of choline esters of N-substituted amino acids under the action of butyrylcholinesterase

Choline esters of N-substituted amino acids: Synthesis and some biological properties

Choline esters of N-substituted amino acids: Synthesis and some biological properties

Multiple conformational equilibria of cyclic octapeptide, cyclo (L-Pro-Sar)4 in solution.

Cyclo (L-Pro-Sar)4 is a synthetic cyclic octapeptide composed of only N-substituted amino acids. The conformation of this peptide in different solvents was examined by 1H- and 13C-n.m.r. spectroscopy. 1H-n.m.r. data of this cyclic peptide demonstrated that multiple conformational equilibria take place in solution and they vary with solvent polarity. Three conformers are interconverting with each other in the nonpolar chloroform (CDCl3); one C4-symmetric conformer (49%) and two C2-symmetric conformers (37% and 14%). While three C2-symmetric (59%, 19%, and 18%) and one asymmetric conformer (4%) are detected to coexist in acetonitrile (CD3CN), one largely populated C2-symmetric one (97%) is favored in the polar dimethyl sulfoxide (Me2SO-d6). N.m.r. measurement employing various strategy predicted the occurrence of trans-cis-cis-cis-trans-cis-cis-cis (two Sar-Pro bonds: trans) (tccctccc) peptide bond sequence in a predominant C2-symmetric conformer of Me2SO-d6 solution. In the same way, tccctccc and ctttcttt (two Sar-Pro bonds: cis) peptide unit arrangement was proposed for the first and the secondly populated conformer in CD3CN, respectively. In CDCl3 a conformer having tctctctc (four Sar-Pro bonds: trans) C4-symmetric peptide bond sequence was deduced.

Thermolysin-catalyzed peptide bond synthesis.

The rates of the thermolysin-catalyzed synthesis of peptides have been determined by means of HPLC. In the condensation of various N-substituted amino acids and peptides with L-leucinanilide, the enzyme exhibits preference for a hydrophobic L-amino acid as the donor of the carbonyl group of the newly formed bond. The presence of another hydrophobic amino acid residue adjacent to the carbonyl-group donor markedly enhances the rate of synthesis. In general, the effect of structural changes in both the carboxyl and amine components of the condensation reaction is in accord with the available data on the primary and secondary specificities of the thermolysin-catalyzed hydrolysis of oligopeptide substrates. A kinetic study of the condensation of benzyloxycarbonyl-L-phenylalanine with various amine components has given data on the apparent kcat and Km values for the entry of the acidic component into the condensation reaction. The results are consistent with the behavior of rapid-equilibrium random bi-reactant systems leading to ternary enzyme-substrate complexes, with a synergistic effect in the binding of the two reactants at the active site. Because the changes in the apparent kcat for the entry of the same acidic component into reaction with different amine components are greater than those in the apparent Km, it is suggested that this synergism is largely expressed at the level of the transition-state complex.

Steady state kinetic evidence for an acyl-enzyme intermediate in reactions catalyzed by bovine spleen cathepsin B.

Cathepsin B from bovine spleen was shown to catalyze transacylation reactions between esters of N-substituted amino acids and nucleophiles. These reactions appeared to proceed through an intermediate between cathepsin B and the acyl portion of the substrate. Of the various nucleophiles tested, dipeptides were found to be the most effective acyl group acceptors. A method was devised for calculating the acylation and deacylation rate constants from increases in the maximum velocity of disappearance of the substrate with increasing concentrations of the nucleophile. The values for the second order rate constants for the reaction of the acyl-enzyme with the nucleophile, k4, were found to depend on the identity of the dipeptide, while the first order rate constants for formation and hydrolysis of the acyl-enzyme, k2 and k3, were dipeptide-independent. With N alpha-benzyloxycarbonyl-L-lysine p-nitrophenyl ester at pH 6.5, k2 and k3 were found to be 360 s-1 and 6.6 s-1, respectively, indicating that the deacylation step was rate-determining for the hydrolysis of this substrate. In contrast, dipeptide nucleophiles did not significantly accelerate the cathepsin B-catalyzed cleavage of either the p-nitroanilide or the 2-naphthylamide of N alpha-benzoylarginine, suggesting that the hydrolysis of these amide substrates was acylation rate-limiting. These findings support the suggestion that cathepsin B is mechanistically similar to the cysteine proteinase papain.

Preparation and Antimicrobial Properties of N-Substituted Amino Acid Type Amphoterics Containing Ether Linkage

Amphoteric surface active N-substituted amino acid derivatives containing long chain alkoxyl radicals and the methylmethylene, ethylene, and methylethylene radicals between amino and carboxyl groups were prepared, then their antimicrobial properties against G. positive, G. negative bacilli and fungi were determined. It was confirmed that N-substituted β-alanine derivatives showed higher antimicrobial properties than the corresponding α-alanine derivatives. The effect of side methyl group between an ammonium and a carboxylate radical was not clear.The surface tension of the N-substituted β-alanine aqueous solution was about 3035dyn/cm in the pH range from 3 to 11.

Identification and localization of two membrane-bound esterases from Escherichia coli.

Hydrolytic activities of isolated membrane fractions of Escherichia coli against chromogenic substrates, p-nitrophenyl ester and beta-naphthyl ester derivatives of N-substituted amino acids, were investigated by spectrophotometric and electrophoretic methods. Although detergents were absolutely necessary for the solubilization of enzymes, the amount of solubilized activities was increased by adding salt, such as NaCl or KCl. Two esterases were identified and separated by PAGE and by chromatography of the solubilized proteins in the presence of detergent. One hydrolyzed the alanine derivatives preferentially, whereas the other was mainly active on phenylalanine derivatives. Only the first was inactivated by diisopropyl fluorophosphate, a serine hydrolase inhibitor. Whereas the chymotrypsin-like enzyme was equally distributed between the inner and the outer membrane, the alanine activity was only detected in the inner membrane. They were both resistant to extraction with high salt concentrations, indicating their integral association with membranes. A study of the accessibility of these enzymes to their substrate in membrane vesicles with known polarity suggests that both alanine and phenylalanine activities are localized near the external surface of the cytoplasmic (inner) membrane. However, the phenylalanine activity (chymotrypsin-like enzyme) appears to be deeply buried inside the outer membrane. Because of its insensitivity to diisopropyl fluorophosphate, this last esterase seems to be distinct from the previously isolated periplasmic endopeptidase, protease I, which is also a chymotrypsin-like enzyme.

Partial molar heat capacity of the peptide group in aqueous solutions.

Integral enthalpies of solution at very high dilution of sodium salts of N-acetyl amino acids, N-acetyl peptides, and N-benzoyl glycine have been measured in water at 298.15 and 308.15 K. Standard heat capacities of solution at 303.15 K have been derived from the enthalpy of solution data. The peptide backbone-unit (CH2CONH) contribution toward the limiting partial molal heat capacities derived from these experimental results is compared with those obtained from Cop2 of other model compounds, viz. oligopeptides, pyrrolidones, piperidones, diketopiperazine, and amides. Cop2 of the peptide backbone unit observed in the sodium slats of the N-substituted amino acids and peptides is also correlated with the structural details of the compounds and it is concluded that Cop2 contribution of the whole CH2CONH group, rather than that of CONH group, should be used for predicting the heat capacities of polypeptides and proteins in aqueous solution.

Synthesis and conformation of cyclic hexapeptide cyclo(Pro-Sar-Sar) 2

A cyclic hexapeptide, cyclo(Pro-Sar-Sar) 2, which consists of N-substituted amino acids only was synthesized, and its solution conformation was investigated by n.m.r. spectroscopy. Seven different C 2-symmetric conformations were detected, which were distinguishable from each other on the n.m.r. time scale. This is due to the cis/trans isomerization of N-substituted peptide bonds. Allowed C 2-symmetric conformations were computed on the basis of a hard-sphere model. Some conformations detected in n.m.r. spectra were not allowed in the calculation. This disagreement suggests that some asymmetric conformations with regard to the single bond rotation are averaged out due to a rapid rotation on the n.m.r. time scale. These points indicate that the molecule of cyclo (Pro-Sar-Sar) 2 is very flexible

The specificity of actinidin and its relationship to the structure of the enzyme

The kinetic parameters k cat , K m and k cat /K m , have been determined for the actinidin-catalysed hydrolyses of N-substituted amino acid esters and amides and compared to the corresponding values for papain (EC 3.4.22.2). Substrates with aromatic N-substituents have lower k cat /K m values for actinidin (EC 3.4.22.14); the difference is much smaller for substrates with aliphatic substituents. The lower k cat /K m values for actinidin generally correspond to higher K m values suggesting that the strength of substrate binding differs between the two enzymes. This difference is explained in terms of the differences in the substrate binding sites found in X-ray crystallographic studies.

Renal transport of amino acids

According to recent experimental data the renal transport of amino acids (AA) is characterized as follows. 1. Kinetics: Several reabsorption systems remove AA from the tubular fluid by active transport with Michaelis-Menten type kinetics. Passive diffusion does play only a relatively small role in reabsorption, but determines the pump leak steady state concentration at the end of the tubule. 2. Stereospecificity: Except for aspartate the naturally occurring L-analogs show a much larger affinity to the transport "carriers" than the D-isomers do. 3. Specificity: Separate transport mechanisms exist for a) the "acidic" AA (Glu and Asp); b) the "dibasic" AA (Arg, Lys, Orn); c) cystine/cystine; d) the "imino" acids (Pro, OH-Pro and other N-substituted AA); e) the beta- and gamma-AA (beta-Ala, GABA, Taurine); f) all other "neutral" AA. For the group (d) and maybe also for (b) and glycine additional low capacity/high affinity systems exist. 4. Localization: Except for glycine and taurine under normal conditions more than 80% of the filtered load are reabsorbed within the first third of the proximal tubule. At an elevated load the rest of the proximal tubule (including pars recta) but not the distal nephron is included into the reabsorptive process. AA are also taken up from the peritubular blood. 5. Energy sources: At least the main part of AA uptake at the brushborder membrane is dependent from a transmembranal Na+-gradient which in turn is established by the ATP driven Na+-pumps at the basolateral side of the cell (Secondary active transport or co-transport of AA). 6. Biochemistry: The biochemical nature of the AA-"carriers" is unknown. The recent hypothesis than a "gamma-glutamyl cycle" plays a major role in this context has been disproved to great extent. 7. Peptides: Oligopeptides (Angiotensin, Gluthathion) filtered at the glomerulum are hydrolyzed by brushborder peptidases within the tubule lumen. The splitting products, the free constituent amino acids, are reabsorbed subsequently by their respective transport systems.

ChemInform Abstract: N‐ACETYL‐DL‐LEUCINATE‐COBALT(II), ‐NICKEL(II) AND ‐ZINC(II) COMPLEXES

AbstractDie durch Umsetzung der Metallperchlorate mit dem Aminosäurederivat in MeOH dargestellten Komplexe (Ia) reagieren mit heterocyclischen Basen im Überschuß zu den Komplexen (Ib) bis (Ie), deren Strukturen durch IR‐ und Elektronenspektren charakterisiert wurden.

N-acetyl-DL-leucinate cobalt(II), nickel(II) and zinc(II) complexes

Complexes of the type M(AcLeu)2 · B2 (M = CoII, NiII or ZnII; B = H2O, py, 3-pic, 4-pic; AcLeu =N-acetyl-DL-leucinate ion) and M(AcLeu)2 B (M = CoII or ZnII and B = o-phen) were prepared and investigated by means of magnetic and spectroscopic measurements. The i.r. spectra of all the complexes are consistent with bidentate coordination of the amino acid to the metal ion. The room temperature solid state electronic spectra indicate that the symmetry of this species is closer toD 4h and that MO6 and MO4N2 chromophores are present in the M(AcLeu)2 · 2 H2O and M(AcLeu)2Bn · x H2O (B = py, 3-pic, 4-pic, n=2 and x=0 for M = NiII; B = o-phen, n=1 and x=0 for M = CoII; B = py, 3-pic, 4-pic, n=1 and x=1 for M = CoII) complexes, respectively. By comparing the Dq values of the amino acid and those of other N-substituted amino acids previously studied, a spectrochemical series of the the cobalt(II) and nickel(II) complexes is proposed. The1 H n.m.r. spectra of the zinc(II) complexes confirm the proposed stereochemistry.

Hydrogen bonding in N-substituted amino acids. Crystal structure of the N,N-diethyl-.beta.-alanine-benzene inclusion compound

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydrogen bonding in N-substituted amino acids. Crystal structure of the N,N-diethyl-.beta.-alanine-benzene inclusion compoundM. A. Peterson, H. Hope, and C. P. NashCite this: J. Am. Chem. Soc. 1979, 101, 4, 946–950Publication Date (Print):February 1, 1979Publication History Published online1 May 2002Published inissue 1 February 1979https://doi.org/10.1021/ja00498a024RIGHTS & PERMISSIONSArticle Views57Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (638 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Study of the aminolysis of the activated esters of N-substituted amino acids by trimethylsilyl derivatives of the amino components

1. Study has been made of the kinetics of the aminolysis of the N-hydroxysuccinimide esters of the Ntert-butyloxycarbonyl derivatives of L-proline and L-leucine by the ethyl esters of L-isoleucine, tert-butylamine and their trimethylsilyt-substituted derivatives, and by the trimethylsilyl ester of N-trimethyl L-isoleucine. 2. Aminolysis by these trimethylsilyl derivatives proceeds through elimination of the N-trimethylsilyl group of the amino component, the reaction rate being considerably lower than that observed with amino components containing a free amino group.

Protease I from Escherichia coli. Some physicochemical properties and substrate specificity.

Protease I, a periplasmic endopeptidase from Escherichia coli has been further purified by a modified procedure. While the purified protein consists of a single polypeptide chain of about 21000 daltons, its molecular weight in dilute salt solution was estimated to be near 43000, suggesting that the enzyme has a marked tendency to dimerize. It has only one disulphide bond and is very sensitive to urea. In agreement with previous evidence of a chymotrypsin-like specificity, hydrolytic assays of various p-nitrophenyl esters of N-substituted amino acids showed that phenylalanine and tyrosine derivatives are the best substrates for the enzyme. The Km(app) for N-benzoyloxycarbonyl-L-tyrosin-p-nitrophenyl ester at pH 7.5 In 100 mM sodium phosphate buffer at 25 degrees C was found to be 0.2 mM. In contrast to chymotrypsin, protease I is unable to hydrolyse N-acetyl-L-phenylalanine ethyl ester and its tyrosine analogue. Moreover, the enzyme appears devoid of amidase activity and exhibits a low activity upon polypeptides. At 37 degrees C, it cleaves the carboxymethylated B-chain of bovine insulin at four points: Phe25-Tyr26, Phe24-Phe25, Leu15-Tyr16 and Ser9-His10. From a detailed study of peptides bonds hydrolyzed, it was concluded that protease I has a stringent requirement for both residues forming the scissile bond, and appears to possess an extended hydrophobic binding site.

Synthesis and Antimicrobial Properties of N-Substituted Amino Acid Type Amphoterics Containing Thioether Linkage

N-Substituted glycine-, alanine- and betaine-type amphoteric surfactants containing long chain alkylthio group were synthesized, and their growth inhibitory activities against Gram positive, Gram negative baccili and some fungi were studied. The effect of the alkylthio group on their antimicrobial and surface activities was compared to that of the alkoxy group of the corresponding N-substituted amino acid amphoterics containing alkoxy group. The obtained N-substituted amino acid amphoterics containing alkylthio group generally, have large antimicrobial powers and excellent surface activities except alanine type derivatives. Dibasic amino acid-type amphoterics having an alkylthio group in the molecule were also tested. Their antimicrobial activities were less than those of the corresponding monobasic amino acid-type amphoterics. Furthermore, N-substituted glycine- and alanine- type amphoteric surfactants, which contained the ether and thioether linkages in the long chain were synthesized and their antimicrobial and surface activities were studied. It is found that the antimicrobial powers of N-substituted amino acid type amphoterics containing alkoxy group is enhanced by introducing an additional thioether group in the molecule.The relative position of ether and thioether group apparently affected their antimicrobial activities.

Antimicrobial Properties of Aminosulf onic Acid Type Amphoterics Containing Ether Linkage

N-Substituted aminosulfonic acid derivatives, ROC2H4N (R') (CH2) 1-2SO3M, R=C10H21, C12H25 R'= H, CH3 M=H, Na, containing long chain alkoxy group were synthesized, and their growth inhibitory activities against Gram positive, Gram negative bacilli and some fungi were compared with those of the N-substituted amino acid derivatives. The introduction of the self onic group instead of the carboxylic group to the N- (2-alkoxyethyl) amino methane or ethane carboxylic acid type amphoterics enhanced their antimicrobial activities. The number of methylene groups between amino and self onic groups influenced their antimicrobial properties, and aminomethanesulf onic acid derivatives showed stronger antimicrobial activities than aminoethanesulfonic acid derivatives. Dodecoxy group was more effective on their antimicrobial properties than the decoxy group. The antimicrobial effect of a methyl group introduced into N atom of the N-alkoxyethylaminomethanesulfonic acid was not so clear as that of a methyl group in the N-substituted amino acid type amphoterics. Moreover, aqueous solution of these amphoterics showed better surface activities at any pH environment,