白腐菌对有机氯农药氯丹的酶促降解特性研究

为了阐明对有机氯农药氯丹具有高效降解能力的白腐菌Phlebia brevispora的酶促降解特性及规律，在实验室条件下，菌株经过纯培养、超声波破碎和高速离心等过程，提取到胞内粗酶液和胞外粗酶液，研究了降解酶对氯丹的降解及其转化特性。结果显示，处理20 min后，胞内酶及胞外酶对10μmol/L氯丹的降解率分别达到33.2%和10.4%。氯丹胞内酶降解的酶促反应最适温度是32℃，最适pH 5.0，最适条件下反应1 h后的氯丹降解率为49.9%。胞内酶在25~40℃，pH 4.5~6.0范围内均具有较高的降解活性；胞内粗酶液的米氏常数Km为3.49μmol/L，最大反应速率Vmax为8.38μmol/min。在胞内酶及胞外酶培养体系分别检测到完全不同的代谢产物。结果表明，氯丹降解酶系包括胞外酶和胞内酶，其中胞内酶是主要降解酶。胞外酶主要催化氯丹的脱氢和脱氯化氢反应，而胞内酶则主要通过羟基化和置换反应将氯丹转化为一些羟基化产物。

Enzymatic Degradation of Organochlorine Insecticide Chlordane by White Rot Fungus

In order to clarify the mechanism of enzymatic degradation organochlorine insecticide chlordane by the white rot fungus Phlebia brevispora, the degradation characteristics of chlordane was determined by the crude enzyme extracted from this strain by pure culture, ultrasonic fragmentation and centrifuge separation. The results showed that, chlordane was degraded about 33.2% and 10.4% by intracellular enzyme and extracellular enzyme within 20 min. At pH 5.0 and 32℃, the crude enzyme showed greatest degradation activity (49.9% ), with its Michaelis-Mentn’s constant (Km) and maximum degradation rate (Vmax) of 3.49μmol/L and 8.38μmol/min, respectively. The results of metabolites analysis indicate that extracellular enzyme can degrade chlordane through dehydrogenation or dehydrochlorination, and intracellular enzyme can transform chlordane to some hydroxylated metabolites through hydroxylation or substitution of chlorine atom by hydroxyl group.