Verkman A S, Skorecki K, Ausiello D A
Proc Natl Acad Sci U S A. 1984 Jan;81(1):150-4. doi: 10.1073/pnas.81.1.150.
Radiation inactivation has been used as a tool to explore the size, structure, and function of soluble and membrane-bound enzymes. Enzyme systems consisting of a single functional unit yield a single exponential dependence of enzyme activity on radiation dose. Complex, nonexponential, inactivation curves suggest the presence of a multiunit enzyme system. A concave-upward inactivation curve suggests the presence of multiple independent functional units of distinct size and activity that do not interact with each other. An oligomeric enzyme, consisting of n identical subunits in equilibrium with monomers, can give simple exponential decay curves or more complex inactivation curves with various degrees of upward or downward concavity, depending upon the extent of oligomer-monomer equilibration among subunits after radiation, oligomer-to-monomer size and activity ratios, and multihit requirements for oligomer inactivation. For each of these possibilities, equations for the inactivation curves are derived, calculated numerically, and discussed in qualitative terms. A systematic approach to the evaluation of complex radiation inactivation curves is proposed and limitations of the radiation inactivation method are reviewed.
辐射失活已被用作一种工具，用于探索可溶性和膜结合酶的大小、结构和功能。由单个功能单元组成的酶系统呈现出酶活性对辐射剂量的单一指数依赖性。复杂的、非指数性的失活曲线表明存在多单元酶系统。向上凹的失活曲线表明存在多个大小和活性不同且互不相互作用的独立功能单元。一种由n个相同亚基与单体处于平衡状态的寡聚酶，根据辐射后亚基间寡聚体 - 单体平衡的程度、寡聚体与单体的大小和活性比以及寡聚体失活的多击要求，可给出简单的指数衰减曲线或具有不同程度向上或向下凹度的更复杂失活曲线。针对这些可能性中的每一种，推导了失活曲线的方程，进行了数值计算，并从定性角度进行了讨论。提出了一种评估复杂辐射失活曲线的系统方法，并对辐射失活方法的局限性进行了综述。
