摘要
对三种固氮蓝藻:固氮鱼腥藻(水生686)、柱孢鱼腥藻和鱼腥藻7120的整细胞及无细胞抽提液的固氮酶活性,进行了比较研究。水生686的整细胞酶活虽然不低(51.9毫米乙烯峰高/光密度/30分),仅次于柱孢鱼腥藻,但其无细胞抽提液的酶活却最低。这可能与它含有大量藻胶有关。研究了Mn^(++)、Fe^(++)对蓝藻固氮酶的作用,以及测定其在不同酶浓度下的反应动力学表明:柱孢鱼腥藻中不存在象深红螺菌中所看到的那种激活因子。用甲苯-乙醇溶液处理藻细胞,对固氮酶作原位测定,探索了它的氧损伤及氧保护机理。
Three species of nitrogen-fixing blue-green algae, Anabaena azotica (HB 686), Anabaenacylindrica and Anabaena 7120, were studied with reference to nitrogenase activity in intactcells as well as in cell-free extracts. Although the nitrogenase activity of intact cells of HB 686(51.9mmC_2H_4/O. D./30min.) was higher than A. 7120 (16.4mmC_2H_4/O. D./30min.), itsactivity in the crude extract was the lowest. This may be due to the abundance of mucilagesin the algal mass. The effects of Mn^(++) and Fe^(++) on the nitrogenase activity of these algae weretudied also, and the reaction kinetics with different enzyme concentrations were estimated. Theresults obtained point out that in A. cylindrica there is a lack of activating cofactor, which hasbeen demonstrated in Rhodospirillum rubrum. Besides, the filaments of Anabaena 7120 weretreated with toluol-ethanol and their N_2-fixing activity in situ was estimated in an attempt tofind out the mechanism of protection from oxygen.
