汞镉对游离和固定化脲酶活性的影响

通过对脲酶与汞镉间关系的研究 ,结果表明 :不同状态 (溶液态、粘粒态和土壤态 )脲酶对汞、镉的反应表现出类似的规律性变化 ,即汞、镉抑制脲酶活性 ,其中汞镉复合污染的影响幅度最大 ,汞的生态毒性最强 ;相关分析显示脲酶活性均可表征样品汞、汞镉污染的程度 ;在汞、镉共存条件下 ,脲酶活性不仅受到汞、镉单因素 ,而且受到它们间交互作用的影响 ,但仍以单独抑制为主 ;由于不同状态脲酶载体的差别 ,导致受影响幅度有较大差异 ,其主要取决于载体对脲酶保护作用和重金属缓冲作用的大小 ,溶液态脲酶无载体 ,而粘粒态和土壤态则相反 ,故溶液态脲酶更易受到重金属的破坏 ,酶的反应也较敏感。温度和尿素浓度均增强了汞镉的抑制作用

EFFECTS OF Hg AND Cd ON FREE AND IMMOBILIZED UREASE ACTIVITY

The relationship of urease activity with Hg and Cd was studied. Results showed a similar effect of Hg and Cd on urease regardless of its state whether solute, clay or soil. Hg Cd's treatment was the highest in inhibition effect when Hg and Cd remarkably inhibited urease activity, meanwhile Hg was the strongest in eco-toxicity. Urease activity could be used as an index of Hg or Hg Cd pollution of the soil. Urease activity was influenced not only by Hg or Cd singly, but also by their interaction. The single-factor effect was still in dominance. Their effects on urease varied sharply because of the difference in its carrier, which plays an important role in protecting the enzyme and buffering the heavy metals. The solute-state urease did not have carriers and hence was more sensitive and susceptible to damage of heavy metals than the other two. Besides, temperature and concentration of urea enhanced the inhibition effect of Hg and Cd on urease activity.