In:
Canadian Journal of Microbiology, Canadian Science Publishing, Vol. 53, No. 2 ( 2007-02), p. 177-185
Abstract:
Chemical modification of carboxyl groups of glucoamylase from a mesophilic fungus, Fusarium solani , was carried out using ethylenediamine as nucleophile in the presence of water-soluble 1-ethyl-3(3-dimethylaminopropyl)carbodiimide. Modification brought about a dramatic enhancement of catalytic activity and thermal stability of glucoamylase. Temperature and pH optima of ethylenediamine-coupled glucoamylase (ECG) increased as compared with those of native enzyme. The specificity constant (k cat /K m ) of native, ECG-2, ECG-11, and ECG-17 was 136, 173, 225, and 170, respectively, at 55 °C. The enthalpy of activation (ΔH*) and free energy of activation (ΔG*) for soluble starch hydrolysis were lower for the chemically modified forms. All of the modified forms werestable at higher temperatures and possessed high ΔG* against thermal unfolding. The effects of α-chymotrypsin and subtilisin on the modified forms were activating as compared with native. Moreover, denaturation of ECG-2, ECG-11, and ECG-17 in urea at 4 mol·L –1 also showed an activation trend. A possible explanation for the thermal denaturation of native and increased thermal stability of ECG-2, ECG-11, and ECG-17 at higher temperatures is also discussed.
Type of Medium:
Online Resource
ISSN:
0008-4166
,
1480-3275
Language:
English
Publisher:
Canadian Science Publishing
Publication Date:
2007
detail.hit.zdb_id:
280534-0
detail.hit.zdb_id:
1481972-7
SSG:
12
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