大豆谷氨酸脱羧酶分离纯化及酶学性质研究

摘要

对大豆中的谷氨酸脱羧酶(GAD)进行了提取、纯化及酶学性质的研究.采用硫酸铵分级沉淀技术对大豆中GAD进行了纯化,该酶被纯化了4.7倍.纯化后的大豆GAD最适温度为40℃,最适pH为5.9,大豆GAD的热稳定性较差,在80℃几乎失去活性,但该酶在pH5.0～8.0较稳定,能保持很好的酶活.大豆GAD对底物谷氨酸的Km值为19.4 mmol/L.Mg2、KCl对大豆GAD活性影响不大,但KI、Ag+、SDS对大豆GAD有抑制作用.Ca2+对大豆GAD有激活作用,当Ca2浓度为1 500 μmol/L时,对大豆GAD激活作用最强,相对酶活能达到160％.大豆GAD与其他植物GAD相比存在差异,并证实可被Ca2+激活.%Glutamate decarboxylase ( GAD) from soybean was extracted and purified, and its character was researched. GAD was purified by 4. 7 - fold from soybean using ammonium sulfate fractionation. The optimal temperature for purified soybean GAD was 40 ℃ and the optimal pH was 5. 9. The thermal stability of soybean GAD was lower, and the enzyme lost all of its activity at 801, but it was stable at pH 5. 0 -8. 0. Km values for glutamic acid was determined as 19. 4 mmol/L. The enzyme was little affected by Mg2 + and KC1, but was distinctly inhibited by KI, Ag+ and SDS. GAD could be activited by Ca2 + , and the comparative activity reached 160% when 1 500 u,mol/L Ca2 + was added.