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  • differential scanning calorimetry  (2)
  • α-chymotrypsin  (2)
  • 1995-1999  (3)
  • 1
    Digitale Medien
    Digitale Medien
    Effects of sorbitol addition on the action of free and immobilized hydrolytic enzymes in organic media (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 406-414 
    Details
    ISSN: 0006-3592
    Schlagwort(e): chymotrypsin ; differential scanning calorimetry ; ligands ; lipase ; organic media ; sorbitol ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effect of the addition of sorbitol on the activity and stability of enzymes was examined by monitoring transesterification reactions performed in organic media at various water activities (aw = 0.08 to 0.97). Lipases from Chromobacterium viscosum and Candida rugosa immobilized on celite, and chymotrypsin, free or immobilized on celite, were used. When the sorbitol-containing enzymes were employed, higher reaction rates and less hydrolysis were observed. Immobilization of chymotrypsin resulted in high activity and operational stability, while the nonimmobilized enzyme was stable only in the presence of sorbitol. The activity of all preparations diminished after washing them with pyridine to remove sorbitol. Furthermore, severe stability problems occurred in the preparations lacking sorbitol. Sorbitol treatment, even after removal of the sorbitol itself, improved the activity of nonimmobilized chymotrypsin relative to the washed control. On the other hand, washing to remove sorbitol had a negative effect on the activity of both coimmobilized lipase and coimmobilized chymotrypsin. Addition of a substrate analogue, N-acetyl-L-phenylalanine, to chymotrypsin yielded a preparation that exhibited higher activity than both the control and its sorbitol-containing counterpart. Differential scanning calorimetry measurements revealed that the chymotrypsin-sorbitol complex was stable against thermal denaturation, undergoing transition at a high temperature (89°C). The transition temperatures of the substrate-containing chymotrypsin and of the control were identical (72°C). © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260450505
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Effects of subzero temperatures on the kinetics of protease catalyzed dipeptide synthesis in organic media (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 429-436 
    Details
    ISSN: 0006-3592
    Schlagwort(e): cryoenzymology ; organic media ; subzero temperature ; peptide synthesis ; α-chymotrypsin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A depeptide synthesis was drastically influenced by the reaction temperature, in the range from -30° to 25°C. This article shows the kinetic reasons of this effect. α-Chymotrypsin was immobilized on celite and used in four different water-miscible solvents containing small amounts of water-miscible solvents containing small amounts of water. The reaction studied was the aminolysis of N-acetyl-L-phenylalanine ethyl ester (Ac-PheOEt) with L-alaninamide (Ala-NH2) and water for the acylenzyme complex, the nucleophile was favoured by low reaction temperatures. This effect (quantified as p-values) was observed in all four solvents, and it was greatest in acetonitrile and tetrahydrofuran. The esterase and amidase activities of the enzyme were studies using AcPheOEt and N-acetyl-L-phenylalanyl-L-ananinamide (AcPheAla-NH2) as substrates. The Michaelis-Menten parameters, Km,app and Vmax, were determined for ester hydrolysis and dipeptide hydrolysis. Both Km,app and Vmax tended to increase with increasing temperature. Secondary hydrolysis was reduced at subzero temperatures because ester hydrolysis was favoured in relation to depeptide hydrolysis. Depeptide synthesis was thus favored by low temperatures in two ways: first, in the competition between the nucleophile and water for the acyl enzyme; and, second, in the competition between the ester substrate and the peptide substrate for the free enzyme. As a result, in acetonitrile containing 10% water, the maximal yield was 99% at -20%C compared with 84% at 25°C. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260460506
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    How do additives affect enzyme activity and stability in nonaqueous media? (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 67-76 
    Details
    ISSN: 0006-3592
    Schlagwort(e): α-chymotrypsin ; buffer salts ; Candida antarctica lipase ; differential scanning calorimetry ; potassium chloride ; sorbitol ; water activity ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The catalytic activities of lyophilized powders of α-chymotrypsin and Candida antarctica lipase were found to increase 4- to 8-fold with increasing amounts of either buffer salts or potassium chloride in the enzyme preparation. Increasing amounts of sorbitol in the chymotrypsin preparation produced a modest increase in activity. The additives are basically thought to serve as immobilization matrices, the sorbitol being inferior because of its poor mechanical properties.Besides their role as supports, the buffer species were indispensable for the transesterification activity of chymotrypsin because they prevented perturbations of the pH during the course of the reaction. Hence, increasing amounts of buffer species yielded a 100-fold increase in transesterification activity. Effects of pH changes were not as predominant in the peptide synthesis and the lipase-catalyzed reactions.Immobilization of the protease on celite resulted in a remarkable improvement of transesterification activity as compared to the suspended protease, even in the absence of buffer species. Immobilization of the lipase caused a small improvement of activity. The activity of the immobilized enzymes was further enhanced 3-4 times by including increasing amounts of buffer salts in the preparation.The inclusion of increasing amounts of sodium phosphate or sorbitol to chymotrypsin rendered the catalyst more labile against thermal inactivation. The denaturation temperature decreased with 7°C at the highest content of sodium phosphate, as compared to the temperature obtained for the denaturation of the pure protein. The apparent enthalpy of denaturation increased with increasing contents of the additives. The enhancement of hydration level and flexibility of the macromolecule upon addition of the compounds partly provides the explanation for the observed results. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 67-76, 1997.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
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