الفهرس 
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Abstract
The present work aimed to investigate the activity level of cyanide hydratase from Cladosporium oxysporum. Phytohormones such as: gibberellic acid (GA3), indole acetic acid (IAA), jasmonic acid, cytokinin, polyamines (e.g. putrescine, spermine, cadaverine, spermidine), their mixture and benzyl adenine stimulated the cyanide hydratase activity in C. oxysporum. Cyanide hydratase was purified to 39.6 unit mg-1 protein; the optimum pH for the free enzyme was 8.0, the optimum temperature for the free enzyme catalysis was 45˚C and the optimum incubation time for enzyme catalysis was 40 min. Ca2+ was the best activator for the enzyme activity where Hg2+ was the most potent inhibitor among the various tested ions. Thiol compounds such as dithiothreitol (DTT), offered variable rate of activation depending on the individual compound and its concentrations. N- ethylmaleimide (NEM) and diethyl pyrocarbonate (DEPC) inhibited the enzyme activity revealing presence of cysteinyl and histidyl groups for enzyme catalysis. Studying the effect of some chelating agents such as o- phenanthroline, α-ά-dipyridyl inhibited the enzyme activity and the
inhibition was concentration dependent. The Km and Vmax values of the
immobilized enzyme were lower than those of the free enzyme. The immobilized cyanide hydratase expressed higher optimal pH and higher optimal temperature compared to the free one. The immobilized enzyme showed storage stability at 4˚C longer than that of the free one. There is a possibility of using cyanide hydratase from C. oxysporum in biodegradation of polluted cyanide.