The effect of heavy metals on peroxidase from Jerusalem artichoke (Helianthus tuberosus L.) tubers

• Published in: African journal of biotechnology 2008-07, Vol.7 (13), p.2248-2253
• Main Author: Sat, I G
• Format: Article
• Language: English
• Subjects: Helianthus tuberosus
• ISSN: 1684-5315; 1684-5315

Peroxidases (EC 1.11.1.7; donor hydrogen peroxide oxidoreductase, POD) are part of a large group of enzymes. In this study, peroxidase, a primer antioxidant enzyme, was partial purified with 2.49 fold and 29.3% efficiency from Jerusalem artichoke (Helianthus tuberosus L.) by ammonium sulphate precipitation and dialysis purification steps. The specific activity of enzyme was calculated as 612.1 EU/mg. The substrate specificity of peroxidase was investigated using 2-methoxyphenol (guaiacol)/hydrogen peroxide (H sub(2)O sub(2)) substrate pattern. Michaelis-Menten constant (K sub(m)) and maximum velocity (V sub(max)) values were calculated from Lineweaver-Burk graph for this substrate pattern. The enzyme had K sub(m) values of 0.263 and 1.143 mM for guaiacol and H sub(2)O sub(2), respectively. The enzyme had V sub(max) of 33.3x10 super(5) and 0.213x10 super(5) EU/mL.min for guaiacol and H sub(2)O sub(2), respectively. Also, the in vitro effect of some heavy metals such as iron (Fe super(2+) and Fe super(3+)), cobalt (Co super(2+)), strontium (Sr super(2+)), zinc (Zn super(2+)), mercury (Hg super(2+)), nickel (Ni super(2+)), aluminium (Al super(2+)) and lead (Pb super(2+)) on POD from Jerusalem artichoke (H. tuberosus) was evaluated. These heavy metals inhibited POD acticity. IC sub(50) values, represents the inhibitor concentration required for obtaining 50% of inhibition of peroxidase. The above mentioned metals had IC sub(50) values of 12.58, 9.48, 12.59, 24.51, 13.57, 7.32, 10.57, 18.69 and 6.00 mM for Fe super(2+), Fe super(3+), Co super(2+), Sr super(2+), Zn super(2+), Hg super(2+), Ni super(2+), Al super(2+) and Pb super(2+), respectively.