الفهرس 
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Abstract
The aims of the present work was to isolate fucoidan and study its bioactivities. Also, it aimed to isolate and characterize fucoidanase from the brown seaweeds. The results were as follow: Fucoidan was found in Colpomenia sinuosa, Sargassum latifolium and Padina pavonica. The highest content was from Colpomenia sinuosa. Fucoidan from Colpomenia sinuosa expressed anticoagulant, antibacterial and antioxidant activities. In addition, it proved to be good inhibitor for alpha-amylase and alpha-glucosidase. Fucoidanase was purified from Colpomenia sinuosa with specific activity of 70 units mg-1 protein using ammonium sulphate, Ca phosphate gel and Sephadex G-200.The optimum pH was 4 and the optimum temperature was 40oC. The Km and Vmax of fucoidanase were 0.95 and 29 units mg-1 protein. The optimum time for fucoidanase catalysis was 20 min. The optimum ATP concentration for enhancing the enzyme was 30 µmol. The optimum DTT concentration for activating the enzyme was 60 µmol. The optimum concentration of cysteine and methionine to enhance the enzyme were 80 and 100 µmol, respectively. The optimum concentrations of thiourea and reduced glutathione for enhancing the enzyme activity were 200 and 80 µmol, respectively. The plant phytohormones IAA, GA3, zeatin riboside and benzyl aminopurine activated the enzyme with optimal concentrations of 40, 40, 60 and 200 µmol, respectively. Treatment of the enzyme with trehalose, BSA and glycol chitosan increased the thermostability of the enzyme. Fucoidanase was stable at 4oC for 70 days. CaSO4 and glycolate activated the enzyme. Treatment of fucoidanase with PGO, NBS, DEPC and DTNB resulted in enzyme inhibition and indicating the essentiality of tyrosyl, tryptophanyl, histidyl and sulfhydryl groups for enzyme catalysis.