McCormick K, Notar-Francesco V J
Biochem J. 1983 Nov 15;216(2):495-8. doi: 10.1042/bj2160495.
Alterations in the long-chain acyl-CoA binding to albumin in the carnitine palmitoyltransferase (CPT) assay appreciably affect the reaction at commonly used substrate concentrations. Since in the CPT assay the latter are typically well below saturation or Vmax. values, the measured enzyme activity depends on both the absolute quantity of albumin in the CPT assay and any biochemical modification of its binding. The present study verifies the striking dependence of the K0.5 for palmitoyl-CoA on albumin and the misleading 'activation' of the enzyme by compounds that also avidly bind to albumin. In assessing the intracellular physiological relevance of any modifier of CPT, the effects of protein binding in the assay assume particular importance. Indeed, any compound that alters CPT activity may do so, not directly, but as an assay artifact changing the free or unbound substrate concentrations.
在肉碱棕榈酰转移酶（CPT）测定中，长链酰基辅酶A与白蛋白的结合改变会在常用底物浓度下显著影响反应。因为在CPT测定中，后者通常远低于饱和浓度或Vmax值，所以测得的酶活性既取决于CPT测定中白蛋白的绝对量，也取决于其结合的任何生化修饰。本研究证实了棕榈酰辅酶A的K0.5对白蛋白的显著依赖性，以及那些也能与白蛋白强烈结合的化合物对该酶具有误导性的“激活”作用。在评估CPT任何调节剂的细胞内生理相关性时，测定中蛋白质结合的影响尤为重要。实际上，任何改变CPT活性的化合物可能并非直接作用，而是作为一种测定假象改变了游离或未结合的底物浓度。
