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Titolo:
Inhibition of chitosan-immobilized urease by slow-binding inhibitors: Ni2+, F- and acetohydroxamic acid
Autore:
Krajewska, B; Zaborska, W; Leszko, M;
Indirizzi:
Jagiellonian Univ, Fac Chem, PL-30060 Krakow, Poland Jagiellonian Univ Krakow Poland PL-30060 c Chem, PL-30060 Krakow, Poland
Titolo Testata:
JOURNAL OF MOLECULAR CATALYSIS B-ENZYMATIC
fascicolo: 4-6, volume: 14, anno: 2001,
pagine: 101 - 109
SICI:
1381-1177(20010706)14:4-6<101:IOCUBS>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
JACK BEAN UREASE; PHOSPHATE BUFFER; MICROBIAL UREASES; BORIC-ACID; MEMBRANE; FLUORIDE; ENZYMES; HYDROLYSIS; BIOSENSOR; DIFFUSION;
Keywords:
urease; chitosan membrane; immobilization; inhibition; Ni2+ ion; F- ion; acetohydroxamic acid;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Krajewska, B Jagiellonian Univ, Fac Chem, Ingardena 3, PL-30060 Krakow, Poland Jagiellonian Univ Ingardena 3 Krakow Poland PL-30060 Poland
Citazione:
B. Krajewska et al., "Inhibition of chitosan-immobilized urease by slow-binding inhibitors: Ni2+, F- and acetohydroxamic acid", J MOL CAT B, 14(4-6), 2001, pp. 101-109

Abstract

The inhibitions by Ni2+ and F- ions and by acetohydroxamic acid of jack bran urease covalently immobilized on chitosan membrane was studied (pH 7.0, 25 degreesC) and compared with those of the native enzyme. The reaction progress curves of the immobilized urease-catalyzed hydrolysis of urea were recorded in the absence and presence of the inhibitors. They revealed that the inhibitions are of the competitive slow-binding type similar to those of native urease. The immobilization weakened the inhibitory effect of the inhibitors on urease as measured by the inhibition constants K-i(*). The increase in their values: 17.9-fold for Ni2+, 26.5-fold for F- and 1.7-fold for acetohydroxamic acid, was accounted for by environmental effects generated by heterogeneity of the urease-chitosan system: (1) mass transfer limitations imposed on substrate and reaction product in the external solution, and (2) the increase in local pH on the membrane produced by both the enzymaticreaction and the electric charge of the support. By relating the K-M/K-i(*) ratio to the electrostatic potential of chitosan it was found that while the reduced Ni2+ inhibition is mainly brought about by the potential, inhibition by acetohydroxamic acid is independent of the potential, and the acidinhibits urease in its non-ionic form. The reduction in F- inhibition was ascribed to the increased pH in the local environment of the immobilized enzyme, (C) 2001 Elsevier Science B.V. All rights reserved.

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Documento generato il 04/04/20 alle ore 20:59:42