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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 117 (1986), S. 1195-1204 
    ISSN: 1434-4475
    Keywords: Carboxamidomethyl ester as C-protecting group ; Enzymatic deprotection ; Peptide synthesis ; α-Chymotrypsin- and Papain-catalyzed peptide bond formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurden die Carboxamidomethylester (CAM-Ester) vonZ- undBoc-geschütztem Alanin und Phenylalanin hergestellt mit dem Ziel, ihre Eignung als Substrate für α-chymotrypsin- und papainkatalysierte Hydrolyse- sowie Peptidsynthesereaktionen zu untersuchen. Die leichte, unter milden Bedingungen und in Abhängigkeit von der Enzymspezifität erfolgende Abspaltung derCAM-C-Schutzgruppe wurde nachgewiesen. An Beispielen wird die proteasekatalysierte Synthese verschiedener Peptidderivate unter Verwendung vonCAM-Estern als C-und N-Komponenten in wäßrig-organischen Medien belegt. Die für die Umsetzungen benötigten Reaktionszeiten sind vergleichsweise gering.
    Notes: Abstract Carboxamidomethyl esters (CAM esters) ofZ- andBoc-protected alanine and phenylalanine were prepared in order to investigate their usefulness as substrates for α-chymotrypsin- and papain-catalyzed hydrolysis and peptide synthesis reactions. The easy removal of theCAM-C-protecting group under mild conditions and dependent on the enzyme specificity was demonstrated. Examples are given for the protease-catalyzed synthesis of various peptide derivatives usingCAM esters as C- and N-components in aqueous-organic media. Comparatively short reaction times were observed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 118 (1987), S. 1279-1288 
    ISSN: 1434-4475
    Keywords: Enzymatic synthesis in biphasic systems ; Peptide synthesis ; α-Chymotrypsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die DipeptidderivateZ-Tyr-Leu-NH2 undMca-Tyr-Leu-NH2 wurden durch α-chymotrypsin-katalysierte Kupplung in biphasischen Systemen aus Puffer und Essigsäureethylester hergestellt. Im Vergleich zu einem rein wäßrigen Medium, in dem nahezu keine Synthese erfolgt, wird in einem biphasischen System die Synthesereaktion durch Extraktion des Dipeptids in die organische Phase wesentlich begünstigt. Es wurde der Einfluß verschiedener Reaktionsparameter, wie Pufferkonzentration, Reaktionszeit, Volumenverhältnis von organischer zu wäßriger Phase und Reaktandenkonzentration auf die Ausbeute anZ-Tyr-Leu-NH2 untersucht. Ein Austausch der hydrophobenZ-Gruppe gegen die hydrophilere Chloracetylgruppe führte zu besseren Dipeptidausbeuten bei höheren Reaktionsgeschwindigkeiten.
    Notes: Abstract The dipeptide derivativesZ-Tyr-Leu-NH2 andMca-Tyr-Leu-NH2 were synthesized by α-chymotrypsin-catalyzed coupling reactions in solvent systems consisting of buffer and ethyl acetate. In comparison to a pure aqueous medium, in which only insignificant synthesis takes place, the product formation is greatly enhanced in a biphasic medium due to extraction of the dipeptide into the organic phase. The influence of several reaction parameters, such as buffer concentration, reaction time, volume ratio of organic and aqueous phase, and reagent concentration on the yield ofZ-Tyr-Leu-NH2 was investigated. Replacement of the hydrophobicZ-group by the more hydrophilic chloroacetyl group resulted in better dipeptide yields at higher reaction rates.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-4475
    Keywords: Enzymic synthesis in biphasic systems ; Peptide synthesis ; α-Chymotrypsin ; Papain ; Thermolysin ; Protected Eledoisin (6–11)-hexapeptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Papain and α-chymotrypsin were used for the protease-catalyzed assembly ofBoc-protected eledoisin (6−11)-hexapeptide by (2+4)- and (3+3)-segment condensation, respectively, in aqueous-organic solvent systems. As C-components, chemically synthesizedBoc-protected peptide methyl esters were employed. The nucleophilic tetrapeptide amide was prepared by papain-catalyzed (2+2)-segment coupling, while theZ-protected C-terminal dipeptide amide could be obtained by α-chymotrypsin- and thermolysin-catalyzed peptide bond formation. In addition, the influence of various reaction conditions, such as solvent composition, nucleophile concentration and reaction time, on the yield of theBoc-protected eledoisin (6−11)-hexapeptide was determined.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 112 (1981), S. 1165-1173 
    ISSN: 1434-4475
    Keywords: Enzymic synthesis in biphasic systems ; Papain-catalyzed peptide bond formation ; Peptide synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Several model peptides have been synthesized enzymatically using papain as a catalyst in biphasic aqueous-organic systems. The effect of different cosolvents,pH, buffer concentration, and reaction time on the papaincatalyzed synthesis was examined. A comparison of the results obtained indicates that water-immiscible organic solvents provide higher yields than methanol in papain mediated peptide synthesis with carboxyl components in the carboxyl free form. Furthermore, it could be established that papaincatalyzed peptide synthesis can be considerably speeded up by employing acyl peptide esters instead of acyl peptides. The former should promote the rapid formation of the acyl-enzyme intermediate.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 112 (1981), S. 469-481 
    ISSN: 1434-4475
    Keywords: Biphasic aqueous-organic solvent mixtures ; α-Chymotrypsin ; Immobilized enzymes ; Peptide synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Kovalent an Kieselgel, Enzacryl AA und Enzacryl AH gebundenes α-Chymotrypsin katalysiert die Peptidbindungsknüpfung zwischen N-geschützten Dipeptid-Methylestern und H-Leu-NH2 mit ähnlichen Ergebnissen wie das freie Enzym. Es wird gezeigt, daß mit Wasser mischbare und nichtmischbare Lösungsmittel, die Trägermaterialien sowie die Struktur der Substrate den Verlauf der Chymotrypsin-katalysierten Kupplungsreaktionen beeinflussen. Die besten Ausbeuten wurden in wäßrig-organischen Zweiphasen-systemen mit Kieselgel-gebundenem Chymotrypsin und mit Substraten mit Leucin in P2-Position erhalten. Die Syntheseausbeuten werden in bezug auf die Reaktivität von Substraten ähnlicher Struktur bei der enzymatischen Hydrolyse diskutiert. Alle immobilisierten Chymotrypsin-Präparationen konnten mit Erfolg für weitere Kupplungsreaktionen wiedergenutzt werden.
    Notes: Abstract α-Chymotrypsin covalently bound to silica, enzacryl AA, and enzacryl AH catalyzes peptide bond formation between N-protected dipeptide methyl esters and H-Leu-NH2 with results similar to those with the free enzyme. The influence of water-miscible and water-immiscible cosolvents, of the supports, and of the structure of the substrates is shown to be of importance for the ease of the chymotrypsin-medicated coupling reactions. The best yields were obtained using biphasic aqueous-organic solvent mixtures, silica-bound chymotrypsin, and substrates with leucine in the P2-position. The yields of the syntheses are discussed in terms of the reactivity of substrates with similar structure in enzymatic hydrolyses. All the immobilized chymotrypsin preparations could be re-utilized successfully for further couplings.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 114 (1983), S. 571-579 
    ISSN: 1434-4475
    Keywords: Enzymic synthesis in biphasic systems ; Pepsin-catalyzed peptide bond formation ; Peptide synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The usefulness of biphasic aqueous-organic solvent systems for pepsin-catalyzed synthesis of model peptidesZ-X-Phe-Phe-OMe (X=Ala, Gln, Leu) has been demonstrated by coupling the correspondingZ-X-Phe-OH with H-Phe-OMe. The influence of various organic solvents on pepsin activity was examined. Some examples are given for the influence of nucleophile and enzyme concentration, bufferpH and organic solvent portion on product yield. Tetrachloromethane and mixtures of ethyl acetate/n-hexane proved to be especially useful allowing syntheses in good yields and within comparatively short reaction times of 2–6 hours.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-4475
    Keywords: Carboxypeptidase Y catalyzed peptide bond formation ; Enzymic synthesis in biphasic systems ; Peptide synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Carboxypeptidase Y katalysiert in einem Zweiphasensystem aus Tetrachlormethan und Carbonatpuffer die Reaktion vonZ-Phe-OMe und verschiedenenZ- undBoc-geschützten Dipeptidmethylestern mit Val-NH2 bzw. Leu-NH2. Nach diesem Verfahren werden die entsprechenden N-geschützen Tripeptidamide in präparativem Maßstab hergestellt. Bei einem Substrat-Nucleophil-Verhältnis von nur 1:2 oder 1:3 erhält man die Peptidderivate in Ausbeuten von 56–97%.
    Notes: Abstract Carboxypeptidase Y catalyzes in a biphasic system containing carbon tetrachloride and carbonate buffer the reaction ofZ-Phe-OMe and variousZ-andBoc-protected dipeptide methyl esters with Val-NH2 and Leu-NH2, respectively. This method has been applied to the synthesis of the corresponding N-protected tripeptide amides on a preparative scale. Using a substrate—nucleophile ratio of only 1:2 or 1:3 the peptide derivatives are obtained in yields of 56–97%.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1434-4475
    Keywords: Immobilized enzymes ; Papain ; Peptide synthesis ; Thermolysin ; Trypsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Model studies were performed on the utility of covalently immobilized trypsin, thermolysin and papain for peptide bond formation. Trypsin and thermolysin catalyzed the formation of peptide bonds with nearly the same efficiency as the soluble proteases and they could be re-used successfully for further coupling experiments. The possibility of using immobilized trypsin and papain for kinetically controlled peptide bond formation was investigated. With the serine type enzyme trypsin excellent product yields were obtained starting with ester carboxyl components and an economical ratio of substrates. Experiments with the thiol protease papain were unsatisfactory because the once formed product is hydrolyzed as fast as the starting ester substrate used.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 283-287 
    ISSN: 1075-2617
    Keywords: Peptide synthesis ; frozen aqueous solution ; ficin ; papain ; clostripain ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The capability of the cysteine proteases ficin, papain and clostripain to form peptide bonds in frozen aqueous solutions was investigated. Freezing the reaction mixture resulted in increased peptide yields in kinetically controlled coupling of Bz-Arg-OEt with various amino acid amides and dipeptides. Under these conditions, peptide yields increased up to 70% depending on the enzyme and the amino component used. Enzyme-catalysed peptide syntheses were carried out under optimized reaction conditions (temperature, amino component concentration and pH before freezing) using the condensation of Bz-Arg-OEt and H-Leu-NH2 as a model reaction.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0570-0833
    Keywords: Enzyme catalysis ; Peptide synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In spite of the enormous progress in the synthesis of peptides and proteins using commercial peptide synthesizers and the immense technological possibilities of recombinant DNA technology, a C—N ligase is an indispensable tool for the racemization-free fragment condensation of peptides. Since activation of the C-terminal α-carboxyl group of a peptide segment could cause partial racemization, chemical condensations of peptide fragments are prone to racemization. For the synthesis of the huge number of peptides and proteins, however, nature has only developed the ribosomal peptidyltransferase, which exhibits its full catalytic function independent of the side-chain functions of the amino acids being coupled. However, its function requires coordination with numerous other ribosomal factors. Besides the limited possibilities of using multienzyme complexes of bacterial peptide synthesis systems, the only alternatives to peptidyltransferase are proteases, which, based on their in vivo function as hydrolases, cannot act as ideal ligases. However, by exploiting the intrinsic reversibility of hydrolytic reactions and by adjusting appropriate physicochemical reaction parameters, the protease acitivity can be used in the direction of ligation. Undoubtedly, the course of kinetically controlled, serine and cysteine protease-catalyzed reactions can be more efficiently influenced than the equilibrium-controlled protease-catalyzed synthesis. This article describes the influence of the enzyme specificity on the efficiency of kinetically controlled synthesis and points the way toward a broad exploitation of serine and cysteine proteases for the catalysis of C—N bond formation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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