Bracho G E, Whitaker J R
Department of Food Science and Technology, University of California, Davis, California 95616.
Plant Physiol. 1990 Feb;92(2):381-5. doi: 10.1104/pp.92.2.381.
Effect of several parameters on inhibition of potato (Solanum tuberosum) invertase by its endogenous proteinaceous inhibitor was determined using homogeneous preparations of both proteins. The inhibitor and invertase formed an inactive complex with an observed association rate constant at pH 4.70 and 37 degrees C of 8.82 x 10(2) per molar per second and a dissociation rate constant of 3.3 x 10(-3) per minute. The inhibitor appeared to bind to invertase in more than one step. Initial interaction (measured by loss of invertase activity) was rapid, relatively weak, readily reversible (K(i) of 2 x 10(-6) molar) and noncompetitive with substrate at pH 4.70. Initial interaction was probably followed by isomerization to a tighter (K(i) of 6.23 x 10(-8) molar) complex, which dissociated slowly with a half-time of 3.5 hour. Interaction between enzyme and inhibitor appeared to be of ionic character and essentially pH independent between pH 3.5 and 7.4.
使用两种蛋白质的均一制剂，测定了几个参数对马铃薯（Solanum tuberosum）转化酶的内源性蛋白质抑制剂抑制作用的影响。该抑制剂与转化酶形成了无活性复合物，在pH 4.70和37℃下观察到的缔合速率常数为8.82×10²/摩尔·秒，解离速率常数为3.3×10⁻³/分钟。该抑制剂似乎以不止一步的方式与转化酶结合。初始相互作用（通过转化酶活性丧失来衡量）迅速、相对较弱、易于逆转（pH 4.70时的抑制常数K(i)为2×10⁻⁶摩尔），且在pH 4.70时对底物无竞争性。初始相互作用之后可能会异构化为更紧密的复合物（抑制常数K(i)为6.23×10⁻⁸摩尔），该复合物以3.5小时的半衰期缓慢解离。酶与抑制剂之间的相互作用似乎具有离子性质，在pH 3.5至7.4之间基本与pH无关。
