Charles S A, Halliwell B
Biochem J. 1980 Mar 1;185(3):689-93. doi: 10.1042/bj1850689.
Freshly purified spinach chloroplast fructose bisphosphatase is powerfully inhibited by inorganic phosphate competitively with respect to its substrate fructose 1,6-bisphosphate. The concentrations of phosphate and substrate in the chloroplast stroma are such that the enzyme in this form could not operate at a significant rate in vivo. Incubation of the enzyme with dithiothreitol for 24 h decreases the Km for fructose 1,6-bisphosphate from 0.8 to 0.033 mM, decreases the Km for Mg2+ from 9 to 2 mM and substantially alleviates inhibition by inorganic phosphate. The physiological significance of thiol activation of the enzyme is discussed.
新鲜纯化的菠菜叶绿体果糖二磷酸酶受到无机磷酸盐的强烈抑制，这种抑制作用是相对于其底物1,6-二磷酸果糖的竞争性抑制。叶绿体基质中磷酸盐和底物的浓度使得这种形式的酶在体内无法以显著的速率发挥作用。将该酶与二硫苏糖醇一起孵育24小时，可使1,6-二磷酸果糖的Km从0.8 mM降至0.033 mM，使Mg2+的Km从9 mM降至2 mM，并基本减轻无机磷酸盐的抑制作用。本文讨论了该酶的巯基激活的生理意义。
