摘要
头状轮生链霉菌(Streptoverticillium caespitosus)谷氨酰胺合成酶(Glutamine synthetase,GS)生物活性的最适pH为7。测活系统中必须加入Mn^(2+)或Mg^(2+),二者分别作激活离子时得到的酶的参数不同。Mn^(2+)对GS有稳定作用。一些金属离子如Ca^(2+)等强烈地抑制生物活性。GS的最适温度为50℃,对ATP、谷氨酸和NH_4Cl的Km值分别为1.75、2.78和5mmol/L。NH_4Cl的浓度小于10mmol/L时对酶有正协同效应,大于10mmol/L时对酶有负协同效应。GS可被氨阻遏,比活能被硝酸盐促进。一些代谢物对GS有累积反馈抑制作用。发酵过程中加入氨后无“氨休克”现象,高氨条件下的GS不受蛇毒磷酸二酯酶(SVPDE)的作用,所以此酶无腺苷酰化—去腺苷酰化调节。
The activity of purified GS was strongly elevated by Mn2+ or Mg2+, where other metabolic ions such as Ca2+, Fe2+, Co2+ were inhibitory. Mn2+ had a pronounced stabilizing effect, so it was incorporated in buffer system for activity study. The optimum pH of GSB was 7, and optimum temperature was 50℃ . Kmvalues of GS for ATP, glutamate and NH4C1 were 1.75,2.78 and 5mmol/ L, respectively. NH4+ exhibitited positive homotropic response when its concentration was lower than 10mmol/L, but give negative homotropic response when its concentration was higher than 10mmol / L. Cumulative feedback inhibition of GS by its metabolites was demonstrated. The enzyme was repressed by NH4+, its specific activity could be increased by nitrate. No phenomenon of 'ammonium shock' appeared after ammonium was added during cultivation, in addition, GS from high ammonium cultures was not affected by SVPDE, so there is no evidence for adenylylation-deadenylylation regulation system for GS of Str. caespitosus.
出处
《微生物学报》
CAS
CSCD
北大核心
1996年第5期367-372,共6页
Acta Microbiologica Sinica
关键词
头状轮生链霉菌
谷氨酰胺合成酶
性质与调节
Streptoverticiilium caespitosus, Glutamine synthetase, Properties and regulation
