Hickman P E, Weidemann M J
Biochem J. 1975 Nov;151(2):327-36. doi: 10.1042/bj1510327.
Pig spleen phosphofructokinase has been purified 800-fold with a yield of 17%. Two isoenzymes that appear to be kinetically identical can be separated by DEAE-cellulose column chromatography. In common with the enzyme from other mammalian sources, the spleen enzyme has a pH optimum of 8.2. At pH 7.0 it displays sigmoidal kinetics with respect to fructose 6-phosphate concentration but its co-operative behaviour is very dependent on pH, protein concentration and the concentration of MgATP. MgGTP and MgITP can replace MgATP as phosphate donors but, unlike MgATP, these nucleotides do not cause significant inhibition. Mn2+ and Co2+ (as the metal ion-ATP complexes) act as cofactors and in the free form are far more inhibitory than free Mg2+. The spleen enzyme responds to a wide variety of potential effector molecules: ADP, AMP, cyclic AMP, aspartate, NH4+, fructose 6-phosphate, fructose 1,6-diphosphate and Pi all act as either activators or protectors, whereas Mg-ATP, Mg2+, citrate, phosphoenol-pyruvate and the phosphoglucerates are inhibitors.
猪脾脏磷酸果糖激酶已被纯化800倍,产率为17%。两种在动力学上似乎相同的同工酶可以通过DEAE - 纤维素柱色谱法分离。与来自其他哺乳动物来源的酶一样,脾脏酶的最适pH值为8.2。在pH 7.0时,它相对于6 - 磷酸果糖浓度呈现S形动力学,但它的协同行为非常依赖于pH值、蛋白质浓度和MgATP的浓度。MgGTP和MgITP可以替代MgATP作为磷酸供体,但与MgATP不同的是,这些核苷酸不会引起明显的抑制作用。Mn2 +和Co2 +(作为金属离子 - ATP复合物)作为辅助因子,其游离形式的抑制作用比游离Mg2 +强得多。脾脏酶对多种潜在的效应分子有反应:ADP、AMP、环AMP、天冬氨酸、NH4 +、6 - 磷酸果糖、1,6 - 二磷酸果糖和Pi都作为激活剂或保护剂起作用,而Mg - ATP、Mg2 +、柠檬酸盐、磷酸烯醇丙酮酸和磷酸甘油酸是抑制剂。