Tryptophan Esters Research Articles

Antioxidation Activities of Amino Acids and Their Esters under the Condition of Active Oxygen Method

Antioxidation activities of 15 amino acids and their benzyl esters (ethyl esters in the case of methionine and tryptophan) on the oxidation of lard or of lard containing natural tocopherol mixture (M-Toc), were examined by means of active oxygen method.All amino acid esters retarded the oxidation of lard containing M-Toc and especially the effects of esters of methionine, lysine, histidine and tryptophan were remarkable, whereas only methionine, phenylalanine, proline and tryptophan among the amino acids examined were fairly effective. Amino acids and their esters themselves, however, showed no antioxidative activities.It was recognized that sodium hydroxide which is strong inorganic base had an intense synergistic effect on M-Toc under conditions without water in this examination, as an incidental result.

Oscillator strengths of the 1La and 1Lb absorption bands of tryptophan and several other indoles.

AbstractThe intensities of the indolyl 1La and 1Lb absorption bands were investigated by using 5‐methoxyindole as a model compound. With 5‐methoxyindole dissolved in weakly interacting solvents, almost the entire 1Lb electronic transition occurs at longer wavelengths than the 1La transition. The resolved spectrum of 5‐methoxyindole permitted estimation of its oscillator strengths and also those of other indoles dissolved in cyclohexane: indole, 0.129 (1La), 0.019 (1Lb); 5‐methylindole, 0.129 (1La), 0.027 (1Lb); 5‐methoxyindole, 0.138 (1La), 0.045 (1Lb); 3‐methylindole and N‐stearyl‐L‐tryptophan n‐hexyl ester, 0.127 (1La), 0.027 (1Lb). Hydrogen bonding to 1‐methyl‐2‐pyrrolidinone does not measurably affect the total near‐ultraviolet oscillator strength of indoles (less than 5% change). In water and ethanol, the oscillator strength of 3‐methylindole and tryptophan is 15–20% less than that of 3‐methylindole dissolved in cyclohexane. The spectra of the N‐stearyl n‐hexyl esters of tryptophan and 1‐methyltryptophan dissolved in methylcyclohexane can be generated by using 1La and 1Lb bands having shapes similar to those observed for 5‐methoxyindole, if the 1La and 1Lb bands are shifted so that their O‐O bands overlap (289.5 nm for tryptophan and 299.5 nm for 1‐methyltryptophan).

Solvent perturbation studies and analysis of protein and model compound data in denaturing organic solvents

For the study of proteins in the denaturing organic alcohols, methanol, ethanol, 1-propanol, trifluoroethanol, and 2-chloroethanol, and the assessment of the number or fraction of exposed tyrosyl and tryptophyl residues in these solvents by the solvent perturbation method of difference spectroscopy, the molar absorbance difference values, Δ ϵλ of the N-acetyl ethyl esters of tyrosine and tryptophan have been obtained with 20% dimethylsulfoxide as a perturbant, and are presented in the 350-260 nm region. Solvent perturbation data obtained on apomyoglobin, serum albumin, and ovalbumin in several of these solvents are presented and analyzed for the purpose of illustration of the computation and curve-fitting techniques used, employing the tabulated model compound data of this paper.

Kinetic properties of the alpha-lytic protease of Sorangium sp., a bacterial homologue of the pancreatopeptidases.

The kinetics under consideration are those of a bacterial serine protease with the same "active serine" sequence as chymotrypsin, trypsin, and elastase, and with a single histidine residue in a sequence which closely matches the sequences around histidine-57 of chymotrypsin and the analogous histidine residues of trypsin and elastase. In agreement with previous evidence of an elastase-like specificity, esters of N-substituted, neutral, aliphatic L-amino acids proved to be good to excellent substrates for the α-enzyme; esters of arginine, tyrosine, and tryptophan were not hydrolyzed. The enzyme has a much higher activity than the pancreatopeptidases towards p-nitrophenyl acetate and p-nitrophenyl trimethyl acetate; the catalytic rate coefficient kc for the latter substrate is about fivefold greater than that of elastase.The catalytic properties match those of the pancreatopeptidases in the following respects. As demonstrated with N-acetyl-L-valine methyl ester as substrate, kc is dependent on an ionization with a pKa of 6.7 in water and 7.3 in H22O; Δ log (kc/Km)/ΔpH for this ionization is equal to 1.0; kc is reduced 50% when H2O is replaced by H22O. These findings are consistent with a requirement for a single unprotonated histidine residue and general basic catalysis by that residue. The burst of p-nitrophenol in hydrolyses of p-nitrophenyl trimethyl acetate is proportional to [E]0; the magnitude of the proportionality factor and the rate of attainment of a steady state are consistent with the condition [Formula: see text], as in chymotrypsin kinetics. Thus the purely catalytic properties of the α-enzyme match those of chymotrypsin very closely. These findings do not support reaction mechanisms which require two catalytically functional histidine residues for such catalysis. The substrate-binding properties of the α-enzyme differ from those of chymotrypsin in that substrate binding does not depend on ionization of an N-terminal α-amino group; Km for the hydrolysis of N-acetyl-L-valine methyl ester is constant from pH 5 to pH 10 and enzymatic activity is unaffected by acetylation of the enzyme's α- and ε-amino groups. Ks for the hydrolysis of p-nitrophenyl trimethyl acetate is appreciably greater than the Ks of elastase for this substrate.The chloromethyl ketones of glycine and valine did not inhibit the enzyme or alkylate its histidine residue.

Guinea pig kallikrein system.

WE have previously shown that the activity of guinea pig γ-globulins as mediators of increased capillary permeability is markedly reduced by soya bean trypsin inhibitor (SBTI) and by di-isopropylphosphofluoridate (DFP)1. Because DFP was inhibitory, we tested esterase activity of guinea pig γ-globulins against synthetic amino-acid esters, using the Roberts2 modification of the Hestrin method. Other workers3 have shown that the enzyme kallikrein isolated from either human urine or plasma hydrolyses esters of arginine (for example, tosylarginine methyl ester, TAMe) specifically, whereas kallikrein isolated from hog pancreas will hydrolyse arginine esters and esters of tyrosine and tryptophan. We found that guinea pig γ-globulins would hydrolyse TAMe and to a smaller extent esters of lysine (for example, lysine methyl ester, LMe) but not esters of tyrosine, tryptophan, leucine or alanine. Furthermore, for four different batches of γ-globulins there appeared to be a relationship between permeability and esterase activities. Permeability activity was measured by intradermal injection into ‘blued’ guinea pigs as described previously1,4.

An enzyme in mast cells with properties like chymotrypsin.

Mast cells contain an enzyme which hydrolyzes 3-chloroacetoxy-2-naphthoic acid anilide. By using highly purified mast cells isolated by differential centrifugation in high density sucrose solutions we have been able to study this enzymatic activity in more detail. The enzyme has properties similar to those of chymotrypsin: Chymotrypsin will hydrolyze the histochemical substrate, and the chymotrypsin and mast cell activities with this substrate are similarly inhibited by diisopropylfluorophosphate. The mast cell enzyme is capable of hydrolyzing the N-acetyl esters of tryptophan, tyrosine, and phenylalanine, the relative rates of hydrolysis being similar to those seen with chymotrypsin. A characteristic trypsin substrate, p-toluenesulfonyl arginine methyl ester, is not acted upon by the mast cell enzyme or chymotrypsin. The pH activity curve of the new cell enzyme is similar to that of chymotrypsin as determined with N-acetyl-L-tryptophan ethyl ester as substrate.

Esterification of adenosine triphosphate by enzymically formed and synthetic tryptophanyl adenylate

If tryptophan-activating enzyme in concentrations approaching substrate level is incubated with tryptophan and ATP, the tryptophan ester in 2′ or 3′ position on the ribose of the ATP is formed. Other nucleotides, when added together with ATP, give similar products. This reaction is considered to be half enzymic and half chemical, and its physiological significance is rather doubtful. An identical ester was obtained by non-enzymic reaction between chemically prepared tryptophanyl adenylate and ATP.