الفهرس 
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Abstract
The present work aimed to isolate and purify choline oxidase from pseudomonas aeruginosa and studying its biochemical characteristics. Also, it aimed to study its active groups and the possible immobilization method. Choline oxidase was purified from pseudomonas aeurginosa by ammonium sulfate (80%), phenyl sepharose and sephadex G-200. The final specific activity was 77.5 Umg-1protein. The purification process was supported by obtaining single band with SDS-PAGE. The thiol compounds DTT and thioglycolate enhanced the enzyme activity. The chelating agents EDTA, dipyridyl and o-phenanthroline inhibited the enzyme indicating that it is a metalloenzyme. Ca2+ was activator for choline oxidase activity whereas Co 2+, Cu2+, Hg2+, Pb2+, Zn 2+ and Ag+ were inhibitors. NBS, BD, DEPC, NAA, dansyl chloride and NEM inhibited the enzyme activity revealing the essentiality of tryptophanyl, arginyl, histidyl, lysyl and SH groups for enzyme catalysis. PEG, dextrose, sucrose, trehalose and raffinose offered protection for the enzyme against heat inactivation. Jasmonic acid, kinetin, gibbrellic acid and naphthalene acetic acid activated the enzyme activity. Choline oxidase was immobilized on alginate and chitosan. The immobilized enzyme exhibited higher optimal temperature, higher thermostability than the free enzyme. The entrapped enzyme was desorbed by SDS with higher rate than cross-linked enzyme.