1. Chemical modification results in hyperactivation and thermostabilization ofFusarium solaniglucoamylase
- Author
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A.M. KhalidA.M. Khalid, Muhammad Asgher, Haq Nawaz Bhatti, Rakhshanda Nawaz, Raheela Perveen, and M. Hamid Rashid
- Subjects
Immunology ,Ethylenediamine ,Fungus ,Applied Microbiology and Biotechnology ,Microbiology ,chemistry.chemical_compound ,Fusarium ,Nucleophile ,Enzyme Stability ,Genetics ,Organic chemistry ,Molecular Biology ,Thermostability ,Binding Sites ,Hyperactivation ,biology ,Temperature ,Chemical modification ,General Medicine ,Hydrogen-Ion Concentration ,biology.organism_classification ,Enzyme Activation ,chemistry ,Biochemistry ,Thermodynamics ,Glucan 1,4-alpha-Glucosidase ,Fusarium solani ,Mesophile - 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 (kcat/Km) 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–1also 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.
- Published
- 2007