镍对花生根瘤菌(Rhizobium arachis)氢酶活性的影响

在吸氢培养基(HuM)和氢气培养下,镍明显地促进了花生根瘤菌(Rhizobiumarachis)L8-3菌株的氢酶活性.5μM NiCl_2能提高吸氢活性两倍以上。螯合剂EDTA和邻菲啰啉抑制氢酶活性,在抑制浓度的螯合剂存在下.加镍可使吸氢活性恢复。除镍外其他二价金属离子如钼、铜、锌、钴、铁、镁、锰、钙等未发现对吸氢活性有促进作用。氢酶活性表达的时间进程受镍的调节,氯霉素阻遏氢酶活性。镍和EDTA对无细胞提取液的氢酶活性不产生影响。研究结果初步认为镍是花生根瘤菌L8-3菌株氢酶活性表达所必需的,可能参与氢酶蛋白的合成。

EFFECT OF NICKEL ON HYDROGENASE ACTIVITY IN RHIZOBIUM ARACHIS

The enhancement of H2-uptake activity in Rhizobium arachis strain L8-3 by nickel was investigated. More than 2-fold stimuation of H2-uptake activity was obtained when cells were grown in the HuM and added 5 μM NiCl2.Chelators, ELTA or O-phenanthroline inhibited the H2-uptake activity.However, the enhancement of H2-uptake activity can be restored when nickel was added in the presence of 100 μM EDTA. The optimum concentration of NiCl2 is 30-50μM for restoring of H2-uptake activity.Other divalent metal elements such as Mo2+,Cu2+, Fe2 + , Mn2+, Zn2+,Co2 + , Mg2 + , Ca2 + could not replace the Ni2+ for restoring the H2-uptake activity in the presence of 100 μM EDTA.Time course of expression of hydrogenase activity showed that the derepression of hydrogenase activity depended on nickel. Chloramphenicol inhibits the hydrogenase activity even in the presence of nickel.However, nickel or EDTA could not affect the H2-uptake activity in crude extract.The evidence indicates that nickel is required for expression of hydrogenase activity in Rhizobium arachis strain L8-3.