降解菌djl-6多菌灵水解酶的提取及性质

以往对多菌灵降解菌Rhodococcus qingshengii sp.nov.djl-6的降解途径研究显示,该菌株首先通过多菌灵水解酶将多菌灵水解成二氨基苯并咪唑,从而对多菌灵进行脱毒.为开发酶制剂并有效应用于环境中残留污染物多菌灵的降解,比较了不同提取方法（高压细胞破碎、超声波破碎和添加溶菌酶破碎）对多菌灵水解酶提取效率的影响,并对其酶学特性进行了初步研究.结果表明,djl-6菌株在LB培养基中培养72~84 h,生长量和产酶量均达到最大值.采用超声波破碎提取酶的效率较高（蛋白浓度为7.92 mg/mL）,但酶活损失较大（比酶活只有1.2 U/μg protein）.多菌灵水解酶属于一种胞内组成型酶.该酶水解多菌灵的最适pH值为7.0,最适温度为30℃,Zn2＋和K＋对酶活有一定的抑制作用.

Hydrolysis mechanism of carbendazim hydrolase from the strain Microbacterium sp.djl-6F

The carbendazim（MBC） hydrolyzing enzyme gene was cloned and heterologously expressed in Escherichia coli BL21（DE3） from a newly isolated MBC-degrading bacterium strain Microbacterium sp. strain djl-6F. High performance liquid chromatography-mass spectrometry（HPLC-MS）analysis revealed that purified MheI-6F protein catalyzes direct hydrolysis of MBC into2-aminobenzimidazole（2-AB） with a high turnover rate and moderate affinity（Kmof6.69 μmol/L and kcatof 160.88/min） without the need for any cofactors. The optimal catalytic condition of MheI-6F was identified as 45°C, pH 7.0. The enzymatic activity of MheI-6F was found to be diminished by metal ions, and strongly inhibited by sodium dodecyl sulfate（SDS）.Through generating amino acid mutations in MheI-6F, Cys16 and Cys222 were identified as the catalytic groups that are essential for the hydrolysis of MBC. This is the first report on the biodegradation of MBC at the enzymatice level.

四川自贡化石木研究

研究了发现于四川省自贡市距著名的大山铺恐龙化石坑０．５～３ｋｍ处的几株化石木。它们的地质时代与大山铺恐龙动物群相同，地层层位大致相当，属于中侏罗世的下沙溪庙组和新田沟组。根据解剖结构特征，确定它们属于原始的松柏类植物———南洋杉型木属中的一个新种，命名为自贡南洋杉型木新种（ＡｒａｕｃａｒｉｏｘｙｌｏｎｚｉｇｏｎｇｅｎｓｉｓＤｕａｎｓｐ．ｎｏｖ．）。化石木的发现对探讨恐龙的生活环境有重要的意义。