Effect of Metal Ions, Chelating Agent and SH-Reagents on Radish (Raphanus sativus L.) Root β-Amylase
Journal Title: Журнал ÑтреÑÑ-физиологии и биохимии - Year 2012, Vol 8, Issue 3
Abstract
Metal ions play vital roles in enzymes. They may also show sensitivity to various sulfhydryl reagents and chelating reagents. Effect of some metal ions, EDTA and sulfhydryl reagents on the activity of partially purified β-amylase of radish root were studied. Amylolytic activity of purified enzyme was increased substantially in the presence of Ca[sup]2+[/sup], Mg[sup]2+[/sup], and Zn[sup]2+[/sup]. Some other divalent cations Cu[sup]2+[/sup], Pb[sup]2+[/sup], Sn[sup]2+[/sup], and Hg[sup]2+[/sup] almost completely ceased the enzyme activity. Cobalt (II), Manganese (II), and Iron (III) exhibited moderate activating effects on the activity. Of the monovalent cations, Na[sup]+[/sup] and Ag[sup]+[/sup] reduced the β-amylase activity, while K[sup]+[/sup] increased. The chelating agent EDTA was found to be effective in the enzyme. Sulfhydryl reagents, Iodoacetic acid and N-Ethylmaleimide showed marginal inhibitory effect, but p-hydroxymercuribenzoic acid (PCMB) almost completely stopped the enzyme activity. The addition of thiol compounds such as cysteine could reverse the inhibitory effect of heavy metals and PCMB. The results indicate that sulfhydryl groups of radish root β-amylase were essential for the activity although it is not clear whether the sulfhydryl groups were directly involved in catalysis.
Authors and Affiliations
M. Sarowar Jahan, S. Dev Sharma, Narayan Roy
Keywords
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