Charles A M, White B
Arch Microbiol. 1976 Jun;108(2):195-202. doi: 10.1007/BF00428951.
Ribulose bisphosphate carboxylase (EC 4.1.1.39) from Thiobacillus A2 has been purified to homogeneity on the basis of polyacrylamide gel electrophoresis and U.V. analysis during sedimentation velocity studies. The enzyme had an optimum pH of about 8.2 with Tris-HCl buffers. The molecular weight was about 521000 with an Srel. of 16.9. Km for RuBP was 122 muM, for total "CO2" it was 4.17 mM, and for Mg2+ 20.0 muM. The absolute requirement for a divalent cation was satisfied by Mg2+ which was replaceable to a certain extent by Mn2+. Activity was not significantly affected by SO(2-4), SO(2-3), or S(2)O(2-3) at 1.0 mM. At this concentration S(2-) caused a 27% stimulation. All mercurials tested were inhibitory. pHMB was the most potent causing about 60% inhibition at 0.04 mM. This inhibition was reversible by low concentrations of cysteine. Cyanide was also inhibitory. Its mode of inhibition with respect to RuBP was un-competitive and with a Ki of 20 muM. Lost activity could be restored partially by GSH or Cu2+. Although azide at the concentration tested had no significant effect on enzyme activity, 2, 4-dinitrophenol at 1.0 mM caused 91% inhibition. Finally, activity was also affected by energy charge.
来自硫杆菌A2的核酮糖二磷酸羧化酶（EC 4.1.1.39）在沉降速度研究过程中，基于聚丙烯酰胺凝胶电泳和紫外分析已被纯化至同质。该酶在Tris-HCl缓冲液中的最适pH约为8.2。分子量约为521000，相对沉降系数为16.9。对核酮糖-1,5-二磷酸（RuBP）的Km为122μM，对总“CO2”为4.17 mM，对Mg2+为20.0μM。二价阳离子的绝对需求由Mg2+满足，Mg2+在一定程度上可被Mn2+替代。1.0 mM的硫酸根离子（SO(2-4)）、亚硫酸根离子（SO(2-3)）或硫代硫酸根离子（S(2)O(2-3)）对活性没有显著影响。在此浓度下，硫离子（S(2-)）引起27%的刺激。所有测试的汞化合物均具有抑制作用。对氯汞苯甲酸（pHMB）最有效，在0.04 mM时引起约60%的抑制。这种抑制作用可被低浓度的半胱氨酸逆转。氰化物也具有抑制作用。其对RuBP的抑制模式是非竞争性的，抑制常数（Ki）为20μM。损失的活性可被谷胱甘肽（GSH）或铜离子（Cu2+）部分恢复。尽管测试浓度的叠氮化物对酶活性没有显著影响，但1.0 mM的2,4-二硝基苯酚引起91%的抑制。最后，活性也受能荷的影响。
