Chelating agents activity test

Maximum activation was observed when the enzyme was tested in the presence of low concentrations of chelating agents such as EDTA (0.5 mM) or histidine (1.0 mM). It is noteworthy that in this case activation was observed with Mg2+ as the activating cation, as well as with Mn2+. It will be recalled that the enzyme treated with FDNB or cystamine showed activation only in the assay with Mn2+ (15, 45). 

Hence, catalytic tests in the hydrodesulfiirization of thiophene showed that the behavior of the catalysts under study depends on the metal-sulfide phase composition and the mode of its formation. The presence of the chelating agents in the impregnating solutions influences both activity and stability of the catalysts. 

No enzyme inhibition has been detected under anoxic conditions as well as in the presence of chelating agents, but the activity was strongly inhibited by 1 mmol Lr1 cathecolic antioxidants, such as a-tocopherol and nordihydroguaretic acid. It is worth recalling that these compounds are also known as inhibitors of lipoxygenase (LOX) activity [22], Several other stress elicitors have been tested, and it has been found that osmotic stress (caused by NaCl and sucrose), heavy metals, heat shock, and membrane-active antibiotics are all able to activate the cis-trans conversion [23,24]. 

Analyses of the enzyme failed to detect significant amounts of iron and copper (Table I), and most metal chelating agents tested did not show significant inhibition of the enzyme activity (JJ). 

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