Simon P, Swillens S, Dumont J E
Biochem J. 1982 Sep 1;205(3):477-83. doi: 10.1042/bj2050477.
Radiation inactivation of complex enzymic systems is currently used to determine the enzyme size and the molecular organization of the components in the system. We have simulated an equilibrium model describing the regulation of enzyme activity by association of the enzyme with a regulatory unit. It is assumed that, after irradiation, the system equilibrates before the enzyme activity is assayed. Our theoretical results show that the target-size analysis of these numerical data leads to a bad estimate of the enzyme size. Moreover, some implicit assumptions such as the transfer of radiation energy between non-covalently bound molecules should be verified before interpretation of target-size analysis. It is demonstrated that the apparent target size depends on the parameters of the system, namely the size and the concentration of the components, the equilibrium constant, the relative activities of free enzyme and enzymic complex, the existence of energy transfer, and the distribution of the components between free and bound forms during the irradiation.
目前，复杂酶系统的辐射失活被用于确定酶的大小以及系统中各组分的分子组织。我们模拟了一个平衡模型，该模型描述了酶与调节单元结合对酶活性的调节作用。假定在辐照后，系统在测定酶活性之前达到平衡。我们的理论结果表明，对这些数值数据进行靶尺寸分析会导致对酶大小的错误估计。此外，在解释靶尺寸分析结果之前，一些隐含假设，如非共价结合分子之间辐射能量的转移，应该得到验证。结果表明，表观靶尺寸取决于系统的参数，即各组分的大小和浓度、平衡常数、游离酶和酶复合物的相对活性、能量转移的存在以及辐照期间各组分在游离和结合形式之间的分布。
