الفهرس 
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Abstract
The aim of the present thesis was to isolate and purify α-glucosidase from P. chrysogenum. The results in the present investigation showed the following:
- The enzyme was isolated and purified using ammonium sulphate, DEAE-cellulose and Sephadex G-200. The final specific activity was 140 units mg-1 protein with 127.3- fold of purification.
- The optimal pH and temperature were 8 and 40ºC. The activation energy was 17.94 KJ mol-1.
- The values of Vmax and Km were 38.1 U mg-1 protein and 0.205 mM, respectively.
- Studying the effect of amino acids on enzyme activity revealed that cysteine, tyrosine, methionine, arginine, asparagine, glutamine and glycine enhanced the enzyme activity with different rates and cysteine was the best.
- The reduced glutathione enhanced α-glucosidase at the lower concentrations and inhibited the activity at the higher ones.
- H2O2 inhibited α-glucosidase activity at all the tested concentrations and the IC50 was 29.2 mM.
- The chelating agents namely EDTA, α-α-dipyridyl and O-phenanthroline inhibited the enzyme activity. The IC50 values for the three compounds were 7.1, 10.2 and 10.9 mM, respectively.
- The thermostability of the enzyme was studied at 60ºC in presence of mannitol and trehalose and the results show that the two compounds offered appreciable stability against heat denaturation.
- Sucrose, glucose, raffinose and lactose offered good thermostability for α-glucosidase at 60ºC.
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- Sarcosine as a derivative of glycine activated the enzyme activity at the higher concentrations.
- The phytohormones such as gibberellic acid, p-amino purine and kinetin enhanced the enzyme activity with variable range at the lower concentrations.
- Dansyl chloride inhibited the enzyme activity at the various tested concentrations indicating the presence of dansyl chloride and its essentiality for enzyme catalysis.
- Ca2+ and Mg2+ were activators whereas Cd2+, Zn2+, Ni2+ and Hg2+ were inhibitors.
- α-glucosidase was immobilized on Ca alginate and the best concentration was 3% w/v for 4h.
- The effect of four different plant extracts on α-glucosidase activity were investigated. These plants were Datura stramonium, Trigonella foenum-graecum, Hyoscymus muticus and Cynodon dactylon. The results revealed to that the four plant extracts exhibited remarkable inhibitory effect on the α-glucosidase particularly Datura extract.